I've started using the browser console window more and more as a calculator. The only downsides are the a longer syntax (eg can't do 3^2) and that it is a tab in the browser. Variables and other such things are very useful.
Why the console window? For basic math things that I sometimes need, I just enter stuff in the search/address bar, and it pops DDG or Google or whatever with the answer; and even your own example of "3^2" works there as-is.
I also often use the browser console for this as well. Just as a quick tip, you can use ** for exponentiation (e.g. 3**2 === 9)
I just have a hotkey that opens a Node CLI. I know some people who do a similar thing with Python, but I think JS is better at composing quick one-liners.