Calculate precise fret positions for guitar and stringed instruments.The unit toggle (inches/mm) doesn't convert—it just changes the display label. The calculator works in whatever unit you enter.
Last updated: March 2026 | By Patchworkr Team
Fret positions on a guitar or other stringed instrument are calculated using the principle of equal temperament, which divides the octave into 12 equal semitones. The placement of each fret must mathematically reduce the vibrating string length by the twelfth root of two (approximately 1.05946).
The scale length is the vibrating length of the string from the nut to the bridge (typically measured to the 12th fret and doubled). Common scale lengths include 25.5" (Fender Stratocaster), 24.75" (Gibson Les Paul), and 25" (PRS guitars). Precise fret placement is critical for proper intonation across the entire fretboard.
Each fret position is calculated from the nut, and the distance between consecutive frets decreases as you move up the neck. This creates the characteristic spacing pattern seen on all properly intonated fretted instruments.
Fret positions are calculated using this formula:
Where n is the fret number (1, 2, 3, etc.)
Fender Stratocaster scale length (25.5 inches):
Note: The 12th fret is always exactly half the scale length (one octave)
Scale length is the vibrating length of the string, measured from the nut to the bridge saddle. It's typically defined as twice the distance from the nut to the 12th fret. Common scales are 25.5" (Fender), 24.75" (Gibson), and 25" (PRS).
Each fret raises the pitch by one semitone, which requires shortening the vibrating string length by the same ratio (twelfth root of 2). Since this ratio is constant but applied to an ever-decreasing length, the physical spacing between frets decreases up the neck.
For proper intonation, fret placement should be accurate to within ±0.005" (0.127mm). Professional luthiers often aim for ±0.002" or better. Even small errors accumulate and cause intonation problems across the fretboard.
Fret compensation accounts for the fact that pressing a string increases its tension and sharpens the pitch. Bridge saddles are set slightly behind the calculated scale length to compensate. This calculator provides theoretical positions from the nut.
Yes! The same equal temperament formula applies to all fretted instruments. Bass guitars typically have longer scale lengths (34" being most common), but the calculation method is identical.
Multi-scale (fanned fret) instruments have different scale lengths for different strings. You would calculate fret positions separately for the bass-side and treble-side scale lengths, then angle the frets between these two positions.
Either works—just be consistent! Many US luthiers use inches, while European makers prefer millimeters. The formula works the same way regardless of units. For precision work, millimeters offer finer resolution.
The 12th fret divides the string exactly in half, producing a note one octave (12 semitones) higher. It's used to verify scale length accuracy: the distance from nut to 12th fret should equal exactly half the scale length.
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