What is guitar scale length?
Nominal scale length is the theoretical reference used to locate the frets. The actual nut-to-saddle speaking length also includes intonation compensation. It determines the mathematical position of every fret and influences string tension and feel.
How do I measure guitar scale length?
Measure from the fretboard-side edge of the nut to the centre of the 12th fret, then double that measurement. This is often more reliable than measuring to an already compensated saddle.
Why measure to the 12th fret?
The 12th fret is the octave and sits at exactly half the theoretical scale length in 12-tone equal temperament. Doubling nut-to-12th gives the nominal full scale.
Where should a guitar bridge be positioned?
Use the scale length as the nominal reference line and make sure the bridge gives each saddle useful adjustment around and beyond it. Real strings need compensation, so final saddle positions are set during intonation—not copied from a single theoretical line.
How are fret positions calculated?
For fret n, the distance from the nut is scale length minus scale length divided by 2 raised to n / 12. Calculations retain full precision internally; displayed measurements are rounded sensibly for workshop use.
Common guitar scale lengths
Common references include 24.75 inches for many traditional short-scale electrics, 25.5 inches for many S- and T-style guitars, extended 27-inch baritone scales and 30- or 34-inch bass scales. Always verify the parts in front of you.