(There's no video for CalcWorks SE yet. Please contribute to MR and add a video now!)
CalcWorks SE is an excessively over-fledged calculator replacement for the truely basic one that came with every Mac OS version.
There are so many options it's overwhelming! Besides calculating, it can convert measurement, mass, temperature, volume, force, power, energy and even currency units... and it comes bundled with the most popular constants such as speed of light, permeability of free space, proton mass, universal gravitation!
If you're looking for a REALLY fully fledged calculator for classic Mac OS versions, then CalcWorks SE is the one.
CalcWorks_1.7.8.sit (229.5 KB)
CalcWorks SE v1.7.8
5 / 2017-02-25
CalcWorks_SE_1.7.6.sit (173.54 KB)
CalcWorks SE v1.7.6 (older)
7 / 2014-04-14 / 2017-02-25
Mac OS 6.x - Mac OS 9.2.2
At least 500KB of free RAM (recommended 1MB)
Emulating this? It should run fine under: SheepShaver