ORIGINAL: karolh
It can be quite confusing for a first timer knowing just what to use as the CG as there is calculated CG and there is also the suggested %f MAC to arrive at a balance point which is significantly different from the CG dimension, all of which can really muddle the water.
With the online calculators, if they can work a yardstick, that's all they need be able to do.
They don't do anything except measure some things, type in the measurements, then hit a key.