Command line math expression evaluator - from the original by Steve Hanov: http://stevehanov.ca/blog/?id=26
The source code that I started with was available on 20 June 2019 at: http://stevehanov.ca/blog/calc.c
This is a simple command line calculator to save you the clicks or keystrokes required by many common options. I think it is the best for simple, rough calculations and it works well for my day-to-day workflow in a Windows environment.

For example;

C:\>ccalc 100/(412117/78221)  
18.980290  
  
C:\>ccalc 0x961
2401.000000
  
C:\>ccalc (3500000 * .03)  
105000.00  
  

In a Linux environment, bc is already available for analygous command line math:

user@host:~$ bc -l <<< "scale=2 ; 100/(412117/78221)"
19.01

(Note the rounding difference. If you are looking for precise results, use tooling purpose built for your needs.)