While you’re developing your skills learning to fly these things, you run across lots of helpful websites. And there are a ton of them. I’ll try to collect as many as I can that I use all the time and post them here for your reference.
eCalc is very popular and is useful for multirotors and helis. Using their calculator, you can find out what size motors and props or blades along with related equipment (ESCs) will give you the most efficient flight. They will ask for donations whenever you click in or out. and frankly, that’s okay. It’s a great resource.
Helicopter Power and set-up Calculator. This headspeed calculator is a lot simpler to use than eCalc and gives great results. Use it to find the right size battery, ESC, motor and pinion for the most efficient flights.
This is one of the first sites I ran across when I started the hobby. Tons of info for beginners. this guy really knows his stuff.
You wanna learn how to fly helicopters? Follow the steps outlined here and you will be a master — if you can manage to make it through the grueling training prescribed in this series flight school classes.