Calculating Fret Scales

by Bob Petrulis

Originally published in Guild of American Luthiers Data Sheet #4, 1974 and Lutherie Woods and Steel String Guitars, 1998



When many of us were starting out, calculating fret scales seemed an arcane and mysterious art, something known to a few high priests of the craft. As kids, we copied scales from existing guitars, or got a list of measurements from a book or by pestering an instrument maker. We did this partly because we knew little of the physics of music, and partly because, back in the dark ages, calculators and computers were not easily available to teenage kids trying to make musical instruments in their basements or in wood shop at school.

This article provides the information you need to calculate any fret scale in any unit of measurement you wish. I am assuming you are calculating a chromatic scale, twelve notes to the octave. If you need to calculate a scale, say, for a dulcimer, I recommend that you calculate the entire fret scale, and then remove the unneeded frets from your listing.