What this fret placement calculator does
This tool calculates fret slot positions for a fretted instrument using standard 12-tone equal temperament (12-TET), which is the modern tuning system used by most guitars, basses, mandolins, and similar instruments. Enter your scale length, choose how many frets you want, and the calculator returns precise distances for each fret.
You get two practical measurements for every fret:
- Distance from nut to fret (best for CNC, templates, and centerline layouts).
- Distance from previous fret (helpful when stepping forward with a rule or indexing jig).
Formula used for fret spacing
Equal temperament equation
For fret number n, measured from the nut:
distance = scaleLength - (scaleLength / 2(n/12))
This is mathematically equivalent to the classic luthier shortcut often called the “rule of 18” (or the more accurate constant 17.817). The equation above is direct, precise, and easy to automate.
How to use it in the shop
- Use the same unit from start to finish (all inches or all millimeters).
- Mark from a single fixed nut reference edge, not from changing points.
- Use sharp layout tools and avoid thick pencil lines for slot locations.
- Double-check fret 12: it should land at exactly half the scale length.
- Keep in mind that compensation is mainly handled at the saddle, not by changing fret math.
Example: 25.5" scale guitar
A 25.5-inch scale is common on many electric guitars. In that setup:
- Fret 12 should be at 12.75 inches from the nut.
- Higher frets get progressively closer together.
- Small layout errors near the nut can noticeably affect intonation.
Common scale lengths
- Guitar (Fender style): 25.5"
- Guitar (Gibson style): 24.75"
- Bass (long scale): 34"
- Bass (short scale): 30"
- Ukulele (concert, approximate): 15"
- Mandolin (common range): about 13.75" to 14"
FAQ
Do I measure to the near edge, center, or far edge of each fret slot?
Layout is usually done to the centerline of each fret. Your saw kerf then straddles that line.
Should I adjust fret spacing for string gauge?
Typically no. Standard fret placement stays fixed. Final intonation adjustments are made at the bridge saddle positions.
Can I use this for fan-fret instruments?
Partially. The math here is for a straight scale on one string path. Multi-scale/fan-fret designs require separate scale lines and angled fret geometry.
Final tip
Precision in fret placement pays off immediately in playability and tuning stability. Whether you are building from scratch or making a custom fretboard template, use exact values, verify your reference points, and cut cleanly.