There is someone on here who has worked out a formula and will tell you know long to cut each one, but I can't remember who it is and I can't find it in the forums. I wish I had a good answer but I usually waste a lot of string because I would rather have them too long than too short. When I first learned I was told to stretch my arm out and cut the string long enough to go from my finger tips to my nose, but it kinda depends on what type of ends you do.