Fret Calculator: Fret Positions from Scale Length
This fret calculator gives you the fret spacing for any instrument: enter the scale length and the number of frets to see each fret’s distance from the nut, from the previous fret and from the bridge, in millimetres and inches.
Example: Scale length (vibrating string length) 648 mm · Number of frets 22 → Result: Fret 22 is 466.16 mm from the nut (scale length 648 mm). Source: Wikipedia – Fret (Abstandsverhältnis 2^(1/12) im gleichstufigen System, Kompensation). Updated: .
How it is calculated
The first fret sits about 5.6% of the scale length from the nut and the twelfth exactly halfway along the string. Every further fret raises the pitch by a semitone, and the spacing shrinks as you go.
How it is calculated
In equal temperament the distances of two neighbouring frets to the bridge are in the ratio 2^(1/12) ≈ 1.0595. That gives the distance of fret n from the nut: s · (1 − 2^(−n/12)), with s the scale length. The calculator also lists the distance to the previous fret and to the bridge, so you can mark the slots step by step or measure from a single reference point.
What it is useful for
- Building a fretboard for a guitar, bass, ukulele or mandolin and marking the fret slots.
- Preparing a fret-slotting template or CNC file with the correct scale length.
- Measuring an existing instrument to find deviations.
Frequently asked questions
How do you calculate fret spacing?
Use distance from the nut = scale length · (1 − 2^(−n/12)), where n is the fret number. With a 648 mm scale the first fret is 36.37 mm from the nut.
Where is the 12th fret?
Exactly halfway along the scale length, so at 324 mm on a 648 mm scale. It produces the octave of the open string.
What is the scale length?
The vibrating string length between the nut and the bridge. It determines fret spacing and string tension.
Why do the frets get closer towards the body?
Because every semitone shortens the string by the same factor. The spacing therefore shrinks by about 5.6% with each fret.
Sources and legal basis
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