A plugin that allows you to run math calcuations without a prefix.

Showcase

$ 10 + 20
30
$ 10 gigabyte / 100 megabyte
100

Installation

zsh-calc relies on an external calculation program.
By default it supports: qalc which has highlighting unit calculations and conversion, physical constants, symbolic calculations, etc;
calc, and bc. You can also configure other calculation programs see configuring. I recommend qalc.

#arch linux
sudo pacman -S libqalculate
# for other distros, search with your package manager for qalculate or qalc

To install the plugin itself, run the install.sh.
To activate the plugin, source it at the bottom of your .zshrc.

...
source /usr/share/zsh/plugins/zsh-calc/zsh-calc.zsh

Configuring

The auto detection system will pick the calculation program in this order:

1. qalc
2. calc
3. bc

To explicitly use a program, set CALC_CMD to one of the values below

#qalc
CALC_CMD="echo \$BUFFER > /tmp/"$USER"qalctemp; qalc -t -c -f /tmp/"$USER"qalctemp"
#calc
CALC_CMD="echo \$BUFFER > /tmp/"$USER"calctemp; calc -f /tmp/"$USER"calctemp"
#bc
CALC_CMD='echo \$BUFFER | bc -l'
# custom
# BUFFER is your command line
CALC_CMD='echo \$BUFFER | CUSTOM_CALC'

Highlighting

If you are using zsh-sytnax-highlight, you can add this regex-highlight to highlight digits:

typeset -A ZSH_HIGHLIGHT_REGEXP
ZSH_HIGHLIGHT_REGEXP+=('[0-9]' fg=cyan)
ZSH_HIGHLIGHT_HIGHLIGHTERS+=(main regexp)

Credits

unix stackexchange post