Calculation options and conventions

Calculation options and conventions

All the choices that determine how the app calculates a schedule, as you find them in the block Calculation profile and options: the profile, the 27 conventions per profile and the calculation options of the project. Why P6 and MS Project calculate differently is in Calculation profiles and conventions; what that means for your dates is in Dates as recorded.

Where to find them and how they work

Choose Settings › Project › Project settings or File › Project settings. At the bottom is the block Calculation profile and options. In the New project window there is only the drop-down Calculation profile: a choice immediately applies the default options of that profile.

Per project, not per app. The profile and the options belong to the project file and travel with Save (IFC). Two people opening the same file therefore calculate the same way. CSV and P6 XML do not carry them; of the calculation options, MS Project XML keeps at most the critical threshold. See Import and export formats. Your own templates are app-wide: the app keeps those on this device.

Only on Apply. What you change in this block is a draft until you click Apply. The app then recalculates the schedule, even if Calculate automatically is off, and, if tasks moved, reports how many (After applying, 3 tasks moved.). If no tasks moved, there is no message. It is one step for Undo. Applying also leaves the view Dates as recorded. A change that changes nothing does nothing. In File › Project settings you throw the draft away with Discard.

Calculation profile

Calculation profile — the basis the app calculates with. Choose from Primavera P6, Microsoft Project and Open Planner Studio, plus your own templates and the custom profile of this project. Default: Open Planner Studio for a new project and for a project without a profile. Effect: the profile switches each of the 27 conventions below on or off. A file you open gets the profile of its format: a .xer calculates as Primavera P6, an .mpp as Microsoft Project, and CSV, MS Project XML and P6 XML as Open Planner Studio. An IFC file keeps the profile stored in it. A built-in profile with deviations from an older file is called Primavera P6 (modified), with the name of the basis. That line stays separate in the list while the project calculates that way. The plain line Primavera P6 is the bare basis, without those deviations; if you choose it, a block says so. If you choose another built-in profile, for example Microsoft Project, the deviations stay as they are: back to Primavera P6 gives them again, also after saving and opening again. If you choose another profile in Project settings, the calculation options stay as they were; if they differ from the default of the new profile, an orange block above the calculation options says so (see Calculation options of this project). Where: the block Calculation profile and options, drop-down Calculation profile.

New profile — makes a custom profile from the chosen profile. Effect: the app asks for a name and suggests Copy of Primavera P6 (or of the profile you started from). Create gives a custom profile with all current values, including the deviations of an older file, and expands Conventions of this profile. An empty name is not possible. The field Name of this custom profile changes the name later; without a name, Apply refuses it. The project uses the new profile only after Apply. Where: next to the list Calculation profile. New project does not show this button.

Ticking or unticking a convention — only in a custom profile. Effect: the profile then deviates from its base. back to base restores the base value. The three built-in profiles are read-only. Where: the part Conventions of this profile.

Save as template, Update template from this project, Update from template and Delete template — manage your custom profiles as a template. Effect: a template is a saved profile that you can choose in any project; the project keeps its own copy. If the profile of the project differs from its template, it says This profile differs from the template “…”. Templates are not in the project file. Save as template reports that the template was saved. If that fails, because there are already 100 templates or because the app storage is full, an error message follows. Delete template asks for confirmation first. Where: below the drop-down, with a custom profile.

Conventions per profile

A convention is a rule in which planning packages differ. Every convention is on or off. The part Conventions of this profile is collapsed by default. Its heading shows the number of conventions and, if the profile deviates, a badge changed: 2. Expanded, the block shows the value per convention and a badge changed: 2 on a group with deviations. The base value (base: on or base: off) is always shown for a custom profile, and for a built-in profile only with a deviation. With a built-in profile the value is a label ON or OFF, for information. With a custom profile it is a tick box, and a deviation has the button back to base. A deviation on a built-in profile comes from an older file. That line has an orange background and a block says that it is used; to change it, use New profile. The i icon after a line shows the explanation: when you point at it with the mouse, on Tab, and on a click or tap. Escape closes only the explanation, not the window below it. A click elsewhere also closes it. When the page scrolls, the explanation of the focused icon stays. If a convention only works with hour planning or only on tasks from a .xer file, a blue label next to the line says so: hour planning only or .xer tasks only. Only with hour planning in the Conditions below means the same as that label: with a calendar with working blocks, for a task whose duration is in hours, or with the Lag calendar set to 24-hour (then a lag counts in hours). The default per convention is what the chosen built-in profile says. Open Planner Studio has every convention off. Under each convention below is what Primavera P6 and Microsoft Project do.

Progress and completed work

Keep actual dates in the backward pass — When calculating backward, a started task keeps its recorded start as its late start, unless In-progress task: early start = start of remaining work is on (as under Primavera P6): then its late start is the start of the remaining work. A completed task keeps its actual dates as its late dates. As a result a completed successor does not pull an open predecessor back into the past. Conditions: Only with a status date. Default: on under Primavera P6, off under Microsoft Project and Open Planner Studio.

In-progress task: early start = start of remaining work — The early and late start of a task in progress point to where the remaining work begins (the later of the status date and the relation boundary), not to the actual start. When calculating backward over a start-to-start relation, only the remaining duration of a predecessor in progress counts; that last part only applies with hour planning. Conditions: Is the basis of the option Calculate SS lag from an in-progress predecessor from and of the convention Elapsed SS lag from an in-progress predecessor does not count. Default: on under Primavera P6, off under Microsoft Project and Open Planner Studio.

Completed physical-progress task sits at the data date — A completed task sits as a single point at the status date, or later if a predecessor requires it, instead of at its actual dates. Conditions: Only with hour planning and with a status date, for completed tasks and milestones from a .xer file with the percent-complete type physical, with an actual finish on or before the status date and without a suspension and resumption (suspend/resume). For other percent-complete types, including the P6 default duration, this has not been measured and the app does not apply it. Requires In-progress task: early start = start of remaining work. Default: on under Primavera P6, off under Microsoft Project and Open Planner Studio.

Planned start is not a floor for a task in progress — The planned start from the file is not a floor for a task in progress (with an actual start and less than 100%): its remaining work begins at the status date, right after its predecessors, even if its planned start is later. This is the counterpart of Planned start as an extra floor. Conditions: Only works if Planned start as an extra floor is on. Default: on under Primavera P6, off under Microsoft Project and Open Planner Studio.

Progress Override ignores a started successor on the late side too — The relation from an uncompleted predecessor to a successor that has already started and is not finished does not count on the late side or in the free float of that predecessor: the successor therefore puts no pressure back and is not a driving relation. Conditions: Only with the progress mode Progress Override. Default: on under Primavera P6, off under Microsoft Project and Open Planner Studio.

Relationships and lag

Successor starts on the finish boundary — A finish-to-start relation without lag whose successor starts exactly at the finish of the predecessor, at the end of a working block, lets the successor begin right at that finish instead of at the start of the next working block. Calculating backward, the successor simply shows its late start as the start of a block. Conditions: Only with hour planning. The file marks nothing: the app recognises such a relation itself when it opens a .xer file. A relation you create yourself does not fall under it. Default: on under Primavera P6, off under Microsoft Project and Open Planner Studio.

Backward lag from a finish boundary — When the app subtracts a working-time lag from the exact finish boundary of a working block while calculating backward and lands exactly on the start of a block, it becomes the finish boundary of the previous block. Also with a finish-to-finish relation without lag, a late finish on a block end stays on that boundary. Conditions: Only with hour planning. Default: on under Primavera P6, off under Microsoft Project and Open Planner Studio.

Elapsed lag of a completed predecessor does not count — Of a positive working-time lag after a completed predecessor only the part that has not yet elapsed at the status date counts: the lag minus the working time between the actual finish and the status date, never less than 0. Conditions: Only with hour planning and with a status date, and only for tasks from a .xer file. Works on the late side and, forward, only from completed predecessors with a status-date point or window (see Completed physical-progress task sits at the data date and Completed out-of-sequence task waits for its predecessors); a completed task that simply sits at its actual dates keeps the full lag. Default: on under Primavera P6, off under Microsoft Project and Open Planner Studio.

Elapsed SS lag from an in-progress predecessor does not count — With a start-to-start relation with a positive working-time lag from a predecessor in progress, only the part of the lag that has not yet elapsed counts: the lag minus the working time between the actual start and the status date, at least 0. Forward that counts from the start of the remaining work of the predecessor; calculating backward, the late start of the predecessor is the late start of the successor minus that remaining lag. Conditions: Only with hour planning. Requires In-progress task: early start = start of remaining work. The option Calculate SS lag from an in-progress predecessor from chooses the starting point. Lags of 0 or less, lags in clock hours and finish-to-start relations stay as usual. Default: on under Primavera P6, off under Microsoft Project and Open Planner Studio.

Early finish not before a finish-to-finish boundary — With a finish-to-finish relation, the early finish of the successor is never before the finish of the predecessor plus the lag. If that boundary falls outside the working time of the successor, the early finish becomes the first working boundary on or after it; the start stays. Conditions: Only with hour planning and with working-time lags; not with a hard finish constraint or a hammock. Default: on under Primavera P6, off under Microsoft Project and Open Planner Studio.

Milestones and LOE activities

Milestone follows the planned calendar boundary — A milestone without duration stays on the calendar boundary that the file planned: a milestone that stood at the start of a day stays a start milestone, and a milestone that stood at the end of a working block may land on the finish of the predecessor. Conditions: Only with hour planning. A task with duration 0 can also stand on two boundaries this way (start on the next block start, finish on the previous block end), but only if it comes from a .xer file and its planned finish is before its planned start. Default: on under Primavera P6, off under Microsoft Project and Open Planner Studio.

Unstarted LOE uses the target window — An LOE activity that has not started (a hammock in the app) with a complete target window takes that target window as its span. Conditions: Only with hour planning, and only if the activity comes from a .xer file with only start-to-start incoming and finish-to-finish outgoing relations without lag. The evidence for this rule is weak: one file. Default: on under Primavera P6, off under Microsoft Project and Open Planner Studio.

Finish-to-finish relationship to a start milestone binds to the milestone itself — A finish-to-finish relation to a start milestone (zero duration, kind Start) binds to the late finish of that milestone itself, instead of to the start of the milestone day. The free float of the predecessor then no longer becomes a working day shorter. The early start of the milestone never changes. Conditions: Only with hour planning; a finish milestone stays unchanged. Default: on under Primavera P6, off under Microsoft Project and Open Planner Studio.

Float and late dates

Free float never negative — With a late constraint that cannot be met, the total float stays negative, but the free float becomes 0 instead of negative. Default: on under Primavera P6, off under Microsoft Project and Open Planner Studio.

Free float in the task's own calendar — The free float of an unstarted task counts per relation in the calendar of the task itself, not in that of the successor. That holds for finish-to-start, start-to-start and finish-to-finish. A relation with a lag (not 0) only falls under it if the lag calendar is Predecessor; otherwise the calendar of the successor stays. A relation without lag always falls under it. A started, uncompleted task only follows this with finish-to-start without lag. Conditions: Only with hour planning. Default: on under Primavera P6, off under Microsoft Project and Open Planner Studio.

Late finish on the task's own calendar — If a successor imposes a late finish that falls outside the working time of the task, the late finish becomes the end of the previous working period on the task's own calendar. A tighter constraint or deadline wins. This is the late-side counterpart of Free float in the task's own calendar. Conditions: Only with hour planning and not for the project finish. Default: on under Primavera P6, off under Microsoft Project and Open Planner Studio.

ALAP tasks as late as the successors allow — An unstarted task with the constraint As late as possible (ALAP) gets as its early finish the strictest boundary that its successors allow with their early dates, to the minute, and as its early start that finish minus its duration. Its own planned window does not count; the floor is its predecessors and the status date. Conditions: Only with hour planning; without hour planning the usual step in whole working days stays. That an ALAP task goes as late as possible and that the successors go first, so that an ALAP chain joins up, holds in every profile, then in whole working days. This convention adds the minute-precise placement from the early dates of the successors. Default: on under Primavera P6, off under Microsoft Project and Open Planner Studio.

Dates and moments from the file

Planned start as an extra floor — The planned start from the file counts as an extra floor next to the network, but only if both start and finish are more than one calendar day later than the network allows. An ordinary start at the next working block does not trigger the rule. Conditions: It does not apply to a task in progress as long as Planned start is not a floor for a task in progress is on; neither does it apply to an unstarted ALAP task that ALAP tasks as late as the successors allow places from its successors. The convention does not look at where the task comes from, only at its planned start and finish. Default: on under Primavera P6, off under Microsoft Project and Open Planner Studio.

Keep actual dates exact — Recorded actual start and finish dates, with their time of day, stay exact and are not moved to the edge of a working block. Conditions: Only for tasks from a .xer file. Default: on under Primavera P6, off under Microsoft Project and Open Planner Studio.

Exact constraint moment on a milestone — A constraint with date and time (SNLT, MSO, FNLT or MFO) on a milestone without duration is an exact point, even if that point is the start of a working block. Conditions: Only with hour planning and on the late side; forward, such a moment is already exact in every profile. Default: on under Primavera P6, off under Microsoft Project and Open Planner Studio.

Progress as in Microsoft Project

Remaining work resumes after the elapsed duration — A task in progress resumes its remaining work at the latest of the status date, the predecessor boundary and the actual start plus the duration that has already elapsed. Under Primavera P6 (Retained Logic) only the first two count; that third floor can only move the remaining work later. Conditions: Not with Progress Override, not when there is no remaining work left and not when the file gives a resume date (Resume) for the task (with at most one assignment). Default: on under Microsoft Project, off under Primavera P6 and Open Planner Studio.

Don't move unstarted tasks to the status date — A task without progress does not shift by itself to on or after the status date. Off applies the floor that P6 does have with Retained Logic. Default: on under Microsoft Project, off under Primavera P6 and Open Planner Studio.

Custom profiles only

These conventions are off in every built-in profile, including Primavera P6. Only a custom profile can switch them on: make one with New profile.

Finish milestone as a boundary window — A finish milestone may stand on two adjacent calendar boundaries: the early start at the start of a working block and the early finish at the end of the previous block. On the late side, a finish milestone without a successor but with predecessors gets its early dates as its late dates and so puts pressure back on its chain, unless Calculate float up to the project finish date is on. Its free float stays the room up to the project finish. Conditions: The boundary window (early start and early finish on two boundaries) only applies if the file planned the milestone that way: planned finish before planned start. The pressure on the chain applies to every finish milestone without a successor. Only seen in P3 output; no effect on files calculated by P6. Default: off in every built-in profile.

Completed task in the data-date window — A completed task gets the status-date window as its early dates, and that window counts towards the project finish and the float. Conditions: Only with a status date, for completed tasks from a .xer file with the percent-complete type duration and the task type Fixed duration and work (in P6: Fixed Duration & Units); no milestones. Requires In-progress task: early start = start of remaining work. Only seen in P3 output. Default: off in every built-in profile.

Completed LOE via its actual finish — A completed LOE activity with only a start-to-start incoming relation and no successor follows the route via its actual finish instead of the usual hammock route. Conditions: Only for tasks from a .xer file; requires In-progress task: early start = start of remaining work, Keep actual dates in the backward pass and Keep actual dates exact. Only seen in P3 output. Default: off in every built-in profile.

Completed predecessor does not hold past the data date — If a completed predecessor ends after the status date according to its actual finish, finish-to-start and finish-to-finish relations calculate from the boundary of the status-date window instead of from that actual finish. Start-to-start relations stay on the actual start. Conditions: Only with hour planning and with a status date. Default: off in every built-in profile.

Completed out-of-sequence task waits for its predecessors — A completed task of which a predecessor is not yet finished (out of sequence) gets its zero-remaining window not at the status date but at the later of the status date and the ordinary relation boundary of that predecessor. Conditions: Only with hour planning. Works on the status-date route of Completed task in the data-date window, so also only for tasks from a .xer file. That convention and In-progress task: early start = start of remaining work must therefore also be on. Not with Progress Override. Default: off in every built-in profile.

Calculation options of this project

These options are under Calculation options of this project, below the conventions. If the applied calculation options of the project differ from the default of the chosen profile, an orange block appears at the top. If you change something in the fields yourself, the block waits until you choose Apply or Discard; otherwise it would name other values than the fields. Choosing another profile updates the block at once. For each difference it names the field, the current value and the default, for example Critical definition: Longest path (default: total float ≤ 0 hours). An empty field counts as the default value that the field shows. For a custom profile the default of its base applies. The button Use the Primavera P6 default settings (with the name of the profile) sets the fields to that default; the app calculates only after Apply, in one step for Undo. The cross hides the block for this opened file. After opening it again, or with a new difference, it comes back. Without a difference there is no block. What the button does with the source options is under Settings from the source file. Defaults per profile: Open Planner Studio and Microsoft Project have no values of their own, so every option is at its default below (for Microsoft Project, Automatic (default) with a status date is also MS Project's own float rule); Primavera P6 sets Lag calendar to Predecessor, Critical definition to Total float ≤ threshold with a threshold of 0 hours, Float calculation to Finish float, Open-ended tasks critical off and Calculate SS lag from an in-progress predecessor from to Remaining start (P6: Early Start). A .xer file also brings values from the file itself.

Critical definition — what makes a task critical. Choose from Total float ≤ threshold and Longest path. Default: Total float ≤ threshold with threshold 0. Effect: with Total float ≤ threshold a task is critical if its total float is less than or equal to the threshold. With Longest path a task is critical if it lies on the chain that leads to the last finish; with several end tasks with the same finish, all their chains count. Float then plays no part. In both cases a completed task is never critical, and neither is a hammock. It applies to the Gantt, the table, the milestone overview and the reports. Where: Calculation options of this project.

Threshold (work days) — the limit for Total float ≤ threshold. Default: 0. Effect: the threshold may be negative. A threshold from a .xer file, or one set by the default of Primavera P6 (0 hours), is in hours and is then called Threshold (hours, per task calendar): the app compares it per task in the hours of that task's calendar. Where: Calculation options of this project, next to Critical definition.

Float calculation — which float the total float is. Choose from Automatic (default), Smallest (start/finish), Start float and Finish float. Default: Automatic (default), also under Microsoft Project; Primavera P6 sets Finish float. Effect: Start float is late start minus early start, Finish float is late finish minus early finish, Smallest (start/finish) is the smaller of the two. Automatic (default) uses the finish float for a task in progress (with an actual start or progress, and a status date) and the smallest for all other tasks. With a status date, that is MS Project's rule. Without a status date, progress does not count and a started task also gets the smallest; MS Project still takes the finish float for a started task then. An opened .mpp file and a new project with Microsoft Project both calculate this way. Smallest (start/finish) takes the smaller one for a task in progress too. Where: Calculation options of this project.

Open-ended tasks critical — a task without a successor. Default: off. Effect: on gives such a task total and free float 0, so that under the critical definition Total float ≤ threshold it becomes critical (unless it is completed). Off calculates the float as usual up to the end of the project. Where: Calculation options of this project.

Mark near-critical — marks tasks with almost no float. Default: off. Effect: on gives a threshold, by default 2 work days (the field Threshold). A task with more than 0 and at most that threshold of total float is called Near critical; a task with exactly 0 float is critical and does not count. You see it in the table column Near critical, in the reports and in the Gantt, where the bar turns amber (unless the task is critical). The field shows work days. With Enable hour planning on it shows hours if the duration display is Always hours, or Automatic (native unit per task) if the project calendar is an hour calendar. Where: Calculation options of this project.

Multiple float paths — numbers chains of tasks by their float. Default: off. Effect: on gives tasks a number in the table column Float path. In the Gantt, bars of path 2 and higher get a tint of their own, unless they are critical or near-critical. Off leaves the column empty. Where: Calculation options of this project.

Method — how the paths arise, with Multiple float paths. Choose from Free float (peeling) and Total float (ranking). Default: Free float (peeling). Effect: with Free float (peeling) the app peels off chains. It picks the task with the last finish and adds its driving predecessors: that is path 1. From the remaining tasks it does the same for path 2, and so on; a shared predecessor keeps the number of the first path in which it occurs. With Total float (ranking) the number is the rank of the task's total float: 1 for the smallest, 2 for the next smallest value. Hammocks do not take part. Where: Calculation options of this project.

Max. paths — how many paths get a number. Default: 10. Effect: tasks outside the first Max. paths paths or ranks get no number. Where: Calculation options of this project, with Multiple float paths.

Lag calendar — in which calendar a lag in working time counts. Choose from Predecessor, Successor, 24-hour and Project calendar. Default: Predecessor. Effect: a lag of 2 days counts in the working days of the calendar you choose. Where: Calculation options of this project. See Relations and lag.

Calculate SS lag from an in-progress predecessor from — the variant of the convention Elapsed SS lag from an in-progress predecessor does not count. Choose from Remaining start (P6: Early Start) and Data date (P6: Actual Start). Default: Remaining start (P6: Early Start). Effect: for a start-to-start relation with a positive working-time lag from a predecessor in progress, the successor with Remaining start (P6: Early Start) starts at the start of the predecessor's remaining work plus the remaining lag. With Data date (P6: Actual Start) it starts at the data date plus the remaining lag, and the relation does not bound the predecessor in progress backward. The remaining lag is the lag minus the working time between the actual start and the data date, never less than 0. A lag of 0 or less, a lag in clock hours and a schedule in days keep the normal behaviour. The choice only works when the conventions Elapsed SS lag from an in-progress predecessor does not count and In-progress task: early start = start of remaining work are both on; otherwise the drop-down is disabled and it says Only applies when the convention “…” is on. If there is no hour planning on the chosen lag calendar, the drop-down is also disabled and it says Only applies with hour planning: a calendar with working blocks or tasks in hours. This project has neither on the chosen lag calendar. There is always hour planning with 24-hour, with Project calendar if the project calendar has working blocks, and with Predecessor and Successor if a calendar of the project has working blocks or a task is in hours. Where: Calculation options of this project.

Settings from the source file

These options come from a Primavera P6 .xer file and are read-only. The block Settings from the source file only appears if the project carries them, so for a project from a .xer file. They count in the calculation. The button Use the … default settings and another profile leave them as the file gave them. They also do not count as a difference. A new project does not get them, not even with Primavera P6.

Use expected finish dates (P6: Use Expected Finish Dates) — Default (if the file says nothing): on. Effect: a P6 task in progress with an expected finish date gets that date as its early finish. Where: Settings from the source file.

Calculate float up to the project finish date — Default: off. Effect: the finish date of the project is the anchor for the late dates. Without a finish date in the file the app calculates up to the end of the network. Where: Settings from the source file.

Completed task: late dates from the data date — Default (if the file says nothing): on. Effect: a completed task also gets zero remaining duration on the data date on the late side, with a meaningful float. It only works together with the convention Completed task in the data-date window, which is off in every built-in profile; if that is off, it says Only works together with the convention “…”, which is currently off. Where: Settings from the source file.

See also

• Calculation profiles and conventions: why P6 and MS Project calculate differently and how a profile works.
• Choosing or building a calculation profile: choose, switch or build a profile.
• Dates as recorded: why an imported schedule can show other dates than your package.
• Critical path and float: what critical, total and free float mean.
• Relations and lag: lag and the calendar in which it counts.
• Progress, status date and baseline: the status date that many conventions refer to.
• Import and export formats: which profile a file gets when it is opened.
• New project and Project settings: the other fields of Project settings and the New project window.