Guitar Fret Calculator (Fret Position from the Nut)

This calculator gives the position of a fret on a guitar or other fretted instrument. Enter the scale length and the fret number; you get the distance from the nut to that fret in inches and millimetres and the distance left from the fret to the saddle.

Formula

d(n) = L − L ÷ 2^(n ÷ 12). Each fret shortens the vibrating string by the factor 2^(1/12), so the 12th fret sits at half the scale length.

• L: scale length, nut to saddle (25.5 in on many electric guitars, 24.75 in on others)
• n: fret number

Worked Example

A 25.5 in scale, fret 12.

1. 2^(12 ÷ 12) = 2
2. d = 25.5 − 25.5 ÷ 2 = 12.750 in
3. In millimetres: 12.75 × 25.4 = 323.85 mm
4. Fret to saddle = 25.5 − 12.75 = 12.750 in

How to read the result

Mark every fret from the nut, not from the previous fret, so small errors do not add up. Real instruments add a little compensation at the saddle for intonation; that does not change the fret positions.

Limits and common mistakes

• The old “rule of 18” (17.817) is an approximation of the same factor; this page uses the exact 2^(1/12).
• Measure scale length from the nut to the 12th fret and double it if you are unsure.

Frequently Asked Questions

Where is the 12th fret?

At exactly half the scale length.

Where is the first fret on a 25.5 in scale?

About 1.431 in from the nut.

What is the rule of 18?

An older approximation, dividing the remaining length by 17.817 for each fret.

Does this work for bass and ukulele?

Yes, for any equal-tempered fretted instrument.

in sl | Scale length | in | 25.5 | 1 | 100
in n | Fret number | - | 12 | 0 | 36
out dist | Nut to fret | in | sl - sl / 2^(n / 12) | 3
out mm | Nut to fret | mm | dist * 25.4 | 2
out rest | Fret to saddle | in | sl - dist | 3