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bcal (Byte CALculator) is a REPL CLI utility for storage expression (e.g. "(2GiB * 2) / (2KiB >> 2)") evaluation, SI/IEC conversion, byte address calculation, base conversion and LBA/CHS calculation. It's very useful for those who deal with bits, bytes, addresses and binary prefixes frequently.

It has a bc mode for general-purpose numerical calculations. Alternatively, it can also invoke the more featured calc which works better with expressions involving multiple bases.

bcal uses SI and IEC binary prefixes and supports 64-bit Operating Systems only.

Table of Contents


  • REPL and single execution modes
  • evaluate arithmetic expressions involving storage units
  • perform general purpose calculations (using bc or calc)
  • works with piped input or file redirection
  • 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 GNU Readline (or BSD Editline). It invokes GNU bc or calc for non-storage expressions.

To use calc:

export BCAL_USE_CALC=1

From a package manager

Install bcal from your package manager. If the version available is dated try an alternative installation method.

Packaging status (expand)

Packaging status

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):

$ sudo make strip install

To link to libedit:

$ sudo make O_EL=1 strip 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:

$ wget
$ unzip
$ 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
            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. 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. r is synced and can be used in expressions. 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. Pipe input.

    $ printf '15 kib + 15 gib \n r / 5' | bcal -m
    $ printf '15 + 15 + 2' | bcal -bm
  9. Redirect from file.

    $ cat expr
    15 gib + 15 kib
    r / 5
    $ bcal -m < expr
  10. Use as a general-purpose calculator.

    $ bcal -b


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 To execute the test cases locally, install pytest and run:

$ make
$ python3 -m pytest

Copyright © 2016 Arun Prakash Jana