Fret Calculator
Enter a scale length to get the exact position of every fret, measured from the nut. For building, refretting, or checking an instrument.
The 12th fret sits at 12.750 in — exactly half the scale length, which is the quickest way to check a measurement.
22 frets on a 25.5 in scale
| Fret | From nut | From previous fret | To bridge |
|---|---|---|---|
| 1 | 1.431 | 1.431 | 24.069 |
| 2 | 2.782 | 1.351 | 22.718 |
| 3 | 4.057 | 1.275 | 21.443 |
| 4 | 5.261 | 1.203 | 20.239 |
| 5 | 6.397 | 1.136 | 19.103 |
| 6 | 7.469 | 1.072 | 18.031 |
| 7 | 8.481 | 1.012 | 17.019 |
| 8 | 9.436 | 0.955 | 16.064 |
| 9 | 10.338 | 0.902 | 15.162 |
| 10 | 11.189 | 0.851 | 14.311 |
| 11 | 11.992 | 0.803 | 13.508 |
| 12 | 12.750 | 0.758 | 12.750 |
| 13 | 13.466 | 0.716 | 12.034 |
| 14 | 14.141 | 0.675 | 11.359 |
| 15 | 14.779 | 0.638 | 10.721 |
| 16 | 15.380 | 0.602 | 10.120 |
| 17 | 15.948 | 0.568 | 9.552 |
| 18 | 16.484 | 0.536 | 9.016 |
| 19 | 16.990 | 0.506 | 8.510 |
| 20 | 17.468 | 0.478 | 8.032 |
| 21 | 17.919 | 0.451 | 7.581 |
| 22 | 18.344 | 0.425 | 7.156 |
Why Frets Get Closer Together
A fret raises a string's pitch by shortening the part that vibrates. To go up a semitone, the vibrating length must shrink by a fixed ratio — to about 94.4% of what it was — not by a fixed distance. As the remaining string gets shorter, 5.6% of it is a smaller distance, so each fret sits closer to the last. By fret 12 the string is half its open length and an octave higher; the next twelve frets then fit into half the space of the first twelve.
On a 25.5" Fender-scale neck:
| Fret | From nut | Millimetres |
|---|---|---|
| 1 | 1.431" | 36.35 mm |
| 5 | 6.397" | 162.47 mm |
| 7 | 8.481" | 215.41 mm |
| 12 | 12.750" | 323.85 mm |
| 24 | 19.125" | 485.77 mm |
Using the Numbers on a Build
- Measure every fret from the nut, not from the previous fret. Measuring fret to fret adds each small error to the next; measuring from one fixed point keeps every slot within the accuracy of your rule.
- Mark the nut edge precisely.All positions are from the face of the nut where the string leaves it. A 0.5 mm error there moves every fret.
- Cut to the centre of the line.The position is the centre of the fret wire's crown, so the slot is centred on the mark.
- Check the 12th. It must be exactly half the scale length. If it is not, re-measure before cutting the rest.
Common Scale Lengths
- 25.5" — Fender Stratocaster and Telecaster, many acoustics and most superstrats. Bright and tight.
- 24.75" — Gibson Les Paul, SG and many Gibson acoustics. Slightly slinkier for bends, warmer in tone.
- 25" — PRS and others, between the two.
- 650 mm — the classical guitar standard.
- 34"— standard bass; 30" for short-scale basses.
- 13", 15", 17" — soprano, concert and tenor ukulele.
Scale length also sets string tension: a longer scale needs more tension to reach the same pitch. The string tension calculator shows how much for any gauge, and once the instrument is strung, the intonation checker tells you whether the saddles need to move.
Frequently Asked Questions
How are fret positions calculated?
Each fret shortens the vibrating string by the same ratio, the twelfth root of two, so each semitone up is the same pitch step. The distance from the nut to fret n is L − L ÷ 2^(n/12), where L is the scale length. Fret 12 lands at exactly half the scale length, an octave above the open string.
What is the rule of 18?
An old luthier's shortcut: divide the remaining string length by 18 to find the next fret. It is close but slightly short, and the error adds up along the neck, so frets drift flat. The precise constant is about 17.817, which is what this calculator effectively uses — it computes each fret directly from the scale length, so errors never accumulate.
How do I measure my scale length?
Measure from the front edge of the nut to the centre of the 12th fret wire, then double it. Measuring nut to saddle gives a slightly longer number, because saddles are set back for intonation compensation.
Where should the bridge go?
At the scale length from the nut, plus compensation: the saddle sits a little further back, more so for thicker strings. On electric guitars with adjustable saddles that is set during intonation. On acoustic guitars a typical starting point is about 2–3 mm extra on the treble side and 4–5 mm on the bass, refined for the strings and action you use.
Does this work for multiscale (fanned-fret) necks?
Calculate the bass-side scale and the treble-side scale separately, then join the matching frets with a straight line. Choose where along the neck the frets are perpendicular — often around the 7th to 9th fret — and align both tables there.