Calculate guitar saddle setback using the simplified Byers intonation formula.
Enter the scale length of your instrument. Standard for electric guitar is 647.7mm (25.5 inches).
Measure the action height at the 12th fret. This affects how much the string stretches when fretted.
The calculator provides the setback offset. You should move the saddle back by this amount from the scale line.
It applies the simplified Byers relation: setback (mm) = action² × π² ÷ (4 × scale length), where action is measured at the 12th fret and both lengths are in millimeters. With the default 647.7 mm (25.5") scale and 2 mm of action it returns 0.0152 mm.
Intonation describes how closely fretted notes match their intended pitch along the whole neck. Pressing a string down to a fret stretches it slightly and raises its tension, pulling the note sharp; setting the saddle back lengthens the vibrating string to cancel that error.
The figure is the theoretical minimum produced by string-stretch geometry alone. As the result note in the tool states, actual compensation may vary with string gauge, action, and string stiffness, so the output serves as a reference value rather than a final saddle position.
Action enters the formula squared, so doubling the 12th-fret action quadruples the offset. On a 647.7 mm scale the output moves from 0.0152 mm at 2 mm of action to 0.0610 mm at 4 mm — exactly a factor of four.
Yes, inversely: scale length sits in the denominator, so a shorter scale yields a slightly larger theoretical setback at the same action. Two millimeters of action gives 0.0157 mm on a 628.65 mm (24.75") scale versus 0.0152 mm on a 647.7 mm scale.
Scale length from 200 mm to 1000 mm and 12th-fret action from 0.5 mm to 10 mm, both entered in millimeters. The saddle setback offset is reported in millimeters to four decimal places.