The Casio FX-991CW Advanced Scientific Calculator is a compact and powerful tool designed for advanced scientific calculations. With its regular display size and pocket-sized design, it is perfect for students and professionals on the go.
Casio FX-991CW the best calculator I have had - so far
Online manual is ok but the pdf version is better.
The physical constants are not explained as to their meaning. Maybe Casio assume if you need the value you'll know the symbol and the units. I noticed at least one value is fractionally different from the latest values.
I hope the next generation of calculators will have units and unit conversions built into the arithmetic e.g. X feet squared times Y psi equals Z kN per metre squared.