On: Soulver – Notepad, meet calculator

[roelschroeven]

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).