I came to the comments to shill for Numi, which is my favorite app for quick calculations. (I don't personally understand why tiled number buttons would ever be desirable for a non-touchscreen GUI app—I much prefer typing equations in.) And I love Numi's variables which you can update and automatically propagate the changes through downstream calculations.
I came to the comments to shill for http://calca.io . For the most part has just worked and have used it in training videos, client emails, rough math sketches, etc. And the output is just markdown-formatted plaintext so you can still use it for reading purposes without the app.
> Functions can also be inverted so that you can solve for their parameters. Note how we were able to use the one equation for Fahrenheit temperatures f to calculate a Celsius temperature c.
This looks really cool. Thanks for the recommendation
