Qalculate! library and CLI
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Qalculate! library and CLI

Image of qalc

Qalculate! is a multi-purpose desktop calculator for GNU/Linux (and Mac OS). It is small and simple to use but with much power and versatility underneath. Features include customizable functions, units, arbitrary precision, plotting, and a user-friendly interface (GTK+ and CLI).

##Installation In a terminal window in the top source code directory run

  • ./ (not required if using a release source tarball, only if using the git version)
  • ./configure
  • make
  • make install (as root) If libqalculate is installed in /usr/local (default) you may need to add /usr/local/lib to the library path of the system (add /usr/local/lib to a file under /etc/ and run ldconfig).


  • CLN - Class Library for Numbers (
  • Libxml2 (>= 2.3.8)
  • Glib
  • Gnuplot 1.7 (optional, for plotting)
  • GVfs or GNU Wget (optional, for retrieval of exchange rates)

##API Documentation The API documentation is included in the package and is installed in $docdir/libqalculate/html (usually /usr/share/doc/libqalculate/html). It is generated when running

It is also available online at

##Using the CLI program 'qalc' To calculate a single expression from the command line (non-interactive mode) enter qalc mathematical expression (e.g. qalc 5+2)

qalc --help shows information about command line options in non-interactive mode.

If you run qalc without any mathematical expression the program will start in interactive mode, where you can enter multiple expressions with history and completion, manipulate the result and change settings. Type help in interactive mode for more information.

##Other Applications The main user interface for libqalculate is qalculate-gtk (

Other software using libqalculate include


  • Calculation and parsing:
    • Basic operations and operators: + - * / ^ E () && || ! < > >= <= != ~ & | << >>
    • Fault-tolerant parsing of strings: log 5 / 2 .5 (3) + (2( 3 +5 = ln(5) / (2.5 * 3) + 2 * (3 + 5)
    • Supports complex and infinite numbers
    • Supports all number bases from 2 to 36, time format and roman numerals
    • Ability to disable functions, variables, units or unknown variables for less confusion: ex. when you do not want (a+b)^2 to mean (are+barn)^2 but ("a"+"b")^2
    • Controllable implicit multiplication
    • Matrices and vectors, and related operations (determinants etc.)
    • Verbose error messages
    • Arbitrary precision
    • RPN mode
  • Result display:
    • Supports all number bases from 2 to 36, plus sexagesimal numbers, time format and roman numerals
    • Many customization options: precision, max/min decimals, multiplication sign, etc.
    • Exact or approximate
    • Fractions: 4 / 6 * 2 = 1.333... = 4/3 = 1 + 1/3
  • Symbolic calculation:
    • Ex. (x + y)^2 = x^2 + 2xy + y^2; 4 "apples" + 3 "oranges"
    • Factorization and simplification
    • Differentiation and integration
    • Can solve most equations and inequalities
    • Customizable assumptions give different results (ex. ln(2x) = ln(2) + ln(x) if x is assumed positive)
  • Functions:
    • All the usual functions: sine, log, etc... : ln 5 = 1.609; sqrt(tan(20) - 5) = sqrt(-2.76283905578)
    • Lots of statistical, financial, geometrical, and more functions (approx. 200)
    • If..then..else function, optional arguments and more features for flexible function creation
    • Can easily be created, edit and saved to a standard XML file
  • Units:
    • Supports all SI units and prefixes (including binary), as well as imperial and other unit systems
    • Automatic conversion: ft + yd + m = 2.2192 m
    • Implicit conversion: 5m/s to mi/h = 11.18 miles/hour
    • Smart conversion: can automatically convert 5 kg*m/s^2 to 5 newton
    • Currency conversion with retrieval of daily exchange rates
    • Different name forms: abbreviation, singular, plural (m, meter, meters)
    • Can easily be created, edit and saved to a standard XML file
  • Variables and constants:
    • Basic constants: pi, e
    • Lots of physical constants and elements
    • CSV file import and export
    • Can easily be created, edit and saved to a standard XML file
    • Flexible, can contain simple numbers, units or whole expressions
    • Data sets with objects and associated properties in database-like structure
  • Plotting:
    • Uses Gnuplot
    • Can plot functions or data (matrices and vectors)
    • Ability to save plot to PNG image, postscript, etc.
    • Several customization options
  • and more...