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Guitar Fret Position Calculator

Calculate exact fret distances from the nut for any scale length, using the standard equal-temperament (12th-root-of-two) fret spacing formula luthiers use.

Distance from nut
324 mm
Distance from bridge
324 mm
Spacing from previous fret
19.27 mm
Fret 12 (half scale length)
324 mm

How it works

Modern fretted instruments space frets using equal temperament: each fret shortens the remaining vibrating string length by the same ratio, the twelfth root of two (≈1.059463), the same ratio that divides an octave into 12 equal semitones. The distance from the nut to fret n is scaleLength × (1 − 1/2^(n/12)).

Because 2^(12/12) = 2 exactly, fret 12 always falls at precisely half the scale length, whatever that scale length is — a useful sanity check when marking out a fretboard by hand. Fret-to-fret spacing (how far apart two adjacent frets sit) is simply the difference between consecutive frets' distances from the nut, and it shrinks steadily as you move up the neck.

This is the exact modern formula, not the older approximate 'Rule of 18' some historical instruments used (dividing the remaining string length by 18 at each fret instead of the more accurate 17.817) — that older rule compounds a small error at each fret and no longer places fret 12 at exactly half scale length.

FAQ

What scale length should I use?

The vibrating string length from the nut to the bridge saddle — common reference values are about 648mm (25.5in) for a Fender-style electric or steel-string acoustic, about 629mm (24.75in) for a Gibson-style electric, and 650mm for a classical guitar, but scale length varies by instrument and model, so measure or look up your specific instrument rather than assuming one of these.

Why doesn't fret 12 land at exactly half scale length on my old instrument?

Older or hand-built instruments sometimes used the historical 'Rule of 18' approximation (dividing remaining string length by 18 at each fret) instead of the exact twelfth-root-of-two calculation. That approximation compounds a small error at each fret, so its fret 12 lands slightly short of true half-scale — one reason the exact formula largely replaced it.

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