I've made fcalc [0] for myself. It's much simpler and basically glorified `eval()`, but it's good enough for me.

[0]: https://fcalc.github.io

You want your calculator to be a web page?

Why not. I use Chrome to make quick calculations all the time. Just Ctrl+N and 1+1, and the answer is posted. Then Ctrl+W, and/or Alt+Tab to Sublime or whatever. Then I continue with my life :)

On macOS, Cmd+Space and just do calculations in the Spotlight search bar.

I also use Windoze, that's why I prefer the Chrome way.

Just a heads up that everything typed into Spotlight is sent to Apple.

Do you have a source for this?

It's in the ToS, and there was a big hoo-haa over it at the time it was introduced. Eg: https://news.ycombinator.com/item?id=8473580

Aside from that, the most basic understanding of what Spotlight is reveals there is no other way for it to function other than to send the users input off-machine:

The user types in a value and results are returned related to that value, some, from online sources.