Inspiration
https://www.figr.app/
Julia? https://discourse.julialang.org/t/physical-units-in-julia/76825
https://numpad.io/
https://soulver.app/
https://cruncher.io/
https://frinklang.org/
https://github.com/printfn/fend
https://www.gnu.org/software/units/manual/units.html
https://heldercorreia.bitbucket.io/speedcrunch/userguide/index.html
https://qalculate.github.io/manual/index.html
https://github.com/PaddiM8/kalker
https://github.com/erhanbaris/smartcalc
https://github.com/bbodi/notecalc3
http://calca.io/ (I keep looking for UI like this because it has easily allowed me to write a series calculations down then copy/paste it into a text doc, email, etc. WITH the calculated results. similar tools (e.g. numpad.io) don't necessarily do this.)