As stated just above, PYFA lets you make simulated characters with various skill levels and lets you plug in any implants and boosters so you can see exactly how your fit will end up and better plan your skill training.
The ingame fitting tool is OK, in fact it has much easier to understand graphical representations of things such as capacitor efficiency, HP/s for tanks, etc. If you are using it don’t forget to use tooltips for things such as tracking, range, etc.