Calculating String Tension

by Max Krimmel

Originally published in Guild of American Luthiers Data Sheet #144, 1980 and Lutherie Woods and Steel String Guitars, 1997



Just how tight is that string? Experience tells most of us that the pitch of a string depends on how long it is, how big it is, and how tight it is. It would seem then, that we could figure out the tension if we know the pitch, mass, and length of any given string. Yes, it can be done. The biggest problem is to realize how A natural, 25.5", and .042" phosphor bronze can be converted into something recognizable as tension. I am not going to go into the why of all this as much as the how to do it. First, put the pitch into cycles per second, or Hz. Next put the length into CM. Then find the mass of the string by weighing a piece of the string as long as your string length. Cut the ball or any other windings off the string before you weigh it on a gram scale. Then insert these variables into the following formula.