I have to agree with Mikro, I could tell you that the scale length is the measurement from the nut to the 12th fret doubled, and on top of that you have to add for the compensation factor, which means that the string length is greater than the scale length.
Knowing the answer to a question is only half of the battle at most, understanding it is much better.
"Make your own electric guitar" , By Melvin Hiscock, is considered by many to be the bible of guitar building, so before you buy any materials you would be wise to buy it.