DIY Instrument Fret Calculator
Place every fret with confidence. Enter your scale length and fret count, then print a template you can tape straight to the neck.
Your build
Measured from the nut contact point to the saddle contact point.
Typical values: 0.3 to 0.8 mm for the nut, 1.5 to 3.5 mm for the bridge.
Results
Fill in your scale length and fret count, then press Calculate.
All numbers appear from the nut unless you turn on compensation.
| Fret | From nut | Spacing | Cumulative |
|---|
Fretboard preview
A scaled preview of your fretboard. The longest fret is closest to the nut. Use this to visualize spacing before you cut.
How the math works
Each fret divides the remaining vibrating length of the string by the twelfth root of two (about 1.059463). That ratio gives equal temperament, where every semitone is the same distance on a logarithmic scale. The formula for fret n is:
This calculator applies that formula for every fret you ask for. When compensation is turned on, it subtracts your nut offset from every distance and adds your bridge offset to the overall scale length. Multi-scale mode runs the same math twice, once for each side, so you can lay out fanned frets with two different scale lengths.
Compensation in practice
When you press a string down, you stretch it slightly. The note sharpens by a few cents unless the string is a tiny bit shorter at the saddle or a tiny bit longer at the nut. Most builders add 1.5 to 3 mm of bridge compensation and 0.3 to 0.8 mm of nut compensation. Heavy strings and high action need more. Start with the defaults here, then fine-tune by ear against a known-good guitar.
Multi-scale and fanned frets
Fanned-fret instruments use a longer scale on the bass side and a shorter scale on the treble side. Each fret is a straight line across the neck, but its distance from the nut is different on each side. The calculator shows both distances per fret, so you can mark each side of the neck separately.
Microtonal and zero-fret setups
If you are building a microtonal instrument, change the division count from 12 to whatever you need. The formula stays the same. For a zero-fret setup, treat the zero fret as your nut and measure every other fret from it. Most builders set the zero fret at the same position a nut would sit, then use this calculator for frets 1 and up.
Instrument presets
| Instrument | Scale length | Frets |
|---|---|---|
| Fender-style guitar | 647.7 mm (25.5 in) | 21 or 22 |
| Gibson-style guitar | 628.7 mm (24.75 in) | 22 |
| Precision bass | 863.8 mm (34 in) | 20 |
| Concert ukulele | 350 mm (13.78 in) | 12 to 15 |
| Mandolin | 329 mm (13 in) | 20 |
| Cigar box guitar | 550 to 650 mm | 19 to 22 |
| Appalachian dulcimer | 660 to 710 mm | 17 to 21 (diatonic) |
Common mistakes and how to avoid them
- Ruler parallax error. Look straight down at the ruler, not from the side. A few degrees of angle can add half a millimeter over a long scale.
- Ignoring wood movement. Humid wood expands and dry wood shrinks. Measure in the room where the instrument will live, not in a garage that changes temperature all day.
- Measuring to the wrong point on the saddle. The vibrating length ends at the contact point, not the back edge of the saddle. On a Tune-o-matic bridge, that is the front of each saddle.
- Forgetting fret tang width. The fret slot itself takes up space. Some builders cut the slot centered on the calculated line. Others offset the slot half a millimeter toward the nut. Pick one method and stay consistent.
- Using stretched or old strings for intonation checks. Fresh strings stabilize faster. Check your intonation with a new set, not a month-old set you just tuned up.
- Printing at the wrong scale. Browser print dialogs love to "fit to page" by default. Turn that off, set scaling to 100 percent, and check the printed output against a ruler before you cut.
When the numbers look wrong
If a calculated fret falls where you do not expect, check your units first. Mixing millimeters and inches is the most common cause of a neck that looks like it was designed for a different planet. Also double-check that you measured your scale length from the right points. Nut-to-saddle is what matters, not nut-to-last-fret or nut-to-bridge-plate.
Printable template
Print the strip below at exactly 100 percent scale. Tape it to your neck, align the zero mark with the nut, and mark each fret line. If the printed strip does not match your ruler, adjust your printer scaling by the percentage difference and print again.
Tip. If you do not have a printer, screenshot the diagram, open it on a phone or tablet, and hold the device behind the neck to check spacing before you commit.