Insect is an open source, high-precision scientific calculator with support for physical units, which I wrote some time ago. There is a version on the web and one for the terminal.

Web version: https://insect.sh/

Your calculation: https://insect.sh/?q=10m%20*%201000kg%20*%209.8m%2Fs%5E2%20t...

Not as polished as Soulver and Numi, but maybe Frink is something for you: https://frinklang.org/

As a student project, I once prototyped a Soulver-like interface that used Frink for its calculations: https://github.com/roryokane/CalcuDoc/wiki/About-CalcuDoc. You can see screenshots and get the code from that link.

I didn’t continue working on it after the class finished, though – I lost all interest after I realized that the Frink programming language, despite being free, is not open source.

this looks awesome, thanks!

Speedcrunch does that, if you don't mind typing it as "10 meter * 1000 kilo gram * 9.8 meter/second^2 in kilo watt hour".

Qalculate! works better for those things: it understands it like you wrote (you have to use "to" instead of "in" for unit conversions though).

You can use GNU units (copy-pasting your text works).