🔢 Storage and general-purpose calculator
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Latest release AUR Homebrew Debian Stretch+ Fedora 27+ Ubuntu Zesty+ Ubuntu PPA

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bcal (Byte CALculator) is a REPL CLI utility for storage expressions, unit conversions or address calculations. If you can't calculate the hex address offset for (512 - 16) MiB, or the value when the 43rd bit of a 64-bit address is set mentally, bcal is for you.

It has a bc mode for general-purpose numerical calculations.

bcal follows Ubuntu's standard unit conversion and notation policy. Only 64-bit operating systems are supported.

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Table of Contents


  • evaluate arithmetic expressions involving storage units
  • perform general purpose calculations (using bc)
  • convert to IEC/SI standard data storage units
  • interactive mode with the last valid result stored for reuse
  • show the address in bytes
  • show address as LBA:OFFSET
  • convert CHS to LBA and vice versa
  • base conversion to binary, decimal and hex
  • custom sector size, max heads/cylinder and max sectors/track
  • minimal dependencies



bcal is written in C and depends on standard libc and libreadline. It invokes GNU bc for non-storage expressions.

From a package manager

Release packages

Packages for Arch Linux, CentOS, Debian, Fedora, OpenSUSE Leap and Ubuntu are available with the latest stable release.

From source

If you have git installed, clone this repository. Otherwise, download the latest stable release or development version (risky).

Install to default location (/usr/local):

$ make
$ sudo make install

To uninstall, run:

$ sudo make uninstall

PREFIX is supported, in case you want to install to a different location.


bcal can be compiled and installed from source in the Termux environment on aarch64 Android devices. Instructions:

$ aria2c https://github.com/jarun/bcal/archive/master.zip
$ unzip bcal-master.zip
$ cd bcal-master/
$ pkg install make clang readline-dev
$ make strip install


cmdline options

usage: bcal [-c N] [-f loc] [-s bytes] [expr]
            [N [unit]] [-b [expr]] [-m] [-d] [-h]

Storage expression calculator.

positional arguments:
 expr       expression in decimal/hex operands
 N [unit]   capacity in B/KiB/MiB/GiB/TiB/kB/MB/GB/TB
            see https://wiki.ubuntu.com/UnitsPolicy
            default unit is B (byte), case is ignored
            N can be decimal or '0x' prefixed hex value

optional arguments:
 -c N       show +ve integer N in binary, decimal, hex
 -f loc     convert CHS to LBA or LBA to CHS
            refer to the operational notes in man page
 -s bytes   sector size [default 512]
 -b [expr]  enter bc mode or evaluate expression in bc
 -m         show minimal output (e.g. decimal bytes)
 -d         enable debug information and logs
 -h         show this help

prompt keys:
 b          toggle bc mode
 r          show result from last operation
 s          show sizes of storage types
 ?          show prompt help
 q/double ↵ quit program

Operational notes

  • Interactive mode: bcal enters the REPL mode if no arguments are provided. Storage unit conversion, base conversion and expression evaluation are supported in this mode. The last valid result is stored in the variable r.
  • Expression: Expression passed as argument in one-shot mode must be within double quotes. Inner spaces are ignored. Supported operators: +, -, *, /, % and C bitwise operators (except ~ due to storage width dependency).
  • N [unit]: N can be a decimal or '0x' prefixed hex value. unit can be B/KiB/MiB/GiB/TiB/kB/MB/GB/TB following Ubuntu policy. Default is byte. As all of these tokens are unique, unit is case-insensitive.
  • Numeric representation: Decimal and hex are recognized in expressions and unit conversions. Binary is also recognized in other operations.
  • Syntax: Prefix hex inputs with 0x, binary inputs with 0b.
  • Precision: 128 bits if __uint128_t is available or 64 bits for numerical conversions. Floating point operations use long double. Negative values in storage expressions are unsupported. Only 64-bit operating systems are supported.
  • Fractional bytes do not exist because they can't be addressed. bcal shows the floor value of non-integer bytes.
  • CHS and LBA syntax:
    • LBA: lLBA-MAX_HEAD-MAX_SECTOR [NOTE: LBA starts with l (case ignored)]
    • CHS: cC-H-S-MAX_HEAD-MAX_SECTOR [NOTE: CHS starts with c (case ignored)]
    • Format conversion arguments must be hyphen separated.
    • Any unspecified value, including the one preceding the first - to the one following the last -, is considered 0 (zero).
    • Examples:
      • c-50--0x12- -> C = 0, H = 50, S = 0, MH = 0x12, MS = 0
      • l50-0x12 -> LBA = 50, MH = 0x12, MS = 0
  • Default values:
    • sector size: 0x200 (512)
    • max heads per cylinder: 0x10 (16)
    • max sectors per track: 0x3f (63)
  • bc variables: scale = 10, ibase = 10. last and r are synced when toggling bc mode. bc is not called in minimal output mode.


  1. Evaluate arithmetic expression of storage units.

    $ bcal "(5kb+2mb)/3"
    $ bcal "5 tb / 12"
    $ bcal "2.5mb*3"
    $ bcal "(2giB * 2) / (2kib >> 2)"
  2. Convert storage capacity to other units and get address, LBA.

    $ bcal 20140115 b
    $ bcal 0x1335053 B
    $ bcal 0xaabbcc kb
    $ bcal 0xdef Gib

    Note that the units are case-insensitive.

  3. Convert storage capacity, set sector size to 4096 to calculate LBA.

    $ bcal 0xaabbcc kb -s 4096
  4. Convert LBA to CHS.

    $ bcal -f l500
    $ bcal -f l0x600-18-0x7e
    $ bcal -f l0x300-0x12-0x7e
  5. Convert CHS to LBA.

    $ bcal -f c10-10-10
    $ bcal -f c0x10-0x10-0x10
    $ bcal -f c0x10-10-2-0x12
    $ bcal -f c-10-2-0x12
    $ bcal -f c0x10-10--0x12
  6. Show binary, decimal and hex representations of a number.

    $ bcal -c 20140115
    $ bcal -c 0b1001100110101000001010011
    $ bcal -c 0x1335053
    bcal> c 20140115  // Interactive mode
  7. Invoke bc.

    $ bcal -b '3.5 * 2.1 + 5.7'
    bcal> b  // Interactive mode
    bc vars: scale = 10, ibase = 10, last = r
    bc> 3.5 * 2.1 + 5.7
  8. Help and additional information.

    $ man bcal
    $ bcal -h


Due to the nature of the project, it's extremely important to test existing functionality before raising any PR. bcal has several test cases written in test.py. To execute the test cases locally, install pytest and run:

$ make
$ python3 -m pytest test.py


Copyright © 2016-2018 Arun Prakash Jana