While APL dialects are very nice for this sort of thing, they generally don't understand units of measure or know about physical constants; you have to put those into them yourself. Here are some of my recent units(1) queries:
141 pounds force 30 mm # in joules
1160/4
log(3)/3/(log(2)/2) # how much more efficient is one-hot ternary than one-hot binary?
5V 7 μs / 7.3 A
.0117% half avogadro mol / 1.251e9 years / (potassium+chlorine)g # how radioactive is lite salt?
3.27$/gallon # in $/liter
sqrt(2 2000 electronvolt/electronmass)
18.8 foot pounds force # in joules
163$/(7.9 g/cc * 1500 mm 3000 mm 3.2 mm) # cold rolled steel price is higher than steel sold by weight
m3/4 / 15 cfh
2 pi sqrt(200 um / gravity)