Calculating Fret Intervals with Spreadsheet Software

by Wayne Kelly

Originally published in American Lutherie #43, 1994



Luthiers who own or have access to a personal computer will find spreadsheet software useful in calculating fret intervals. Spreadsheet software is commonly used for accounting, budgeting, and presentation of tabular data. It is invaluable for testing “what if” scenarios because a change made to one cell of a spreadsheet will cause a “ripple effect,” automatically changing values in other cells dependent on that cell. This feature of spreadsheet software makes it possible to calculate fret intervals for a given scale length instantly. Change the scale length value and “presto,” another set of fret intervals is automatically and instantly calculated and displayed. Results can be printed if desired. Within a few minutes one could create a book of fret interval tables for dozens of different scale lengths.

I created a spreadsheet to calculate fret intervals using the “fret factors” found in a popular textbook on guitar building (Cumpiano, William R. and Natelson, Jonathan D., Guitarmaking: Tradition and Technology, Rosewood Press, Maine, 1987, p. 268). With fret factors, each fret’s distance from the nut is determined by simply multiplying the fret’s factor by the chosen scale length. My spreadsheet allows one to enter a given scale length, expressed in decimal inches, and it then calculates and displays the distance from the nut to each of 21 frets, as shown in the accompanying figure. The fret intervals are displayed in three columns expressed in centimeters, decimal inches, and sixty-fourths of an inch, respectively.