Same instrument. Five different fret counts. See and hear the range.

Pick a configuration below. The fretboard renders with geometrically accurate spacing — frets really do get closer together as you climb, exactly the way they do on a real guitar. Tap the play button to hear a chromatic ascent up the high E string to the topmost fret.

Each note one semitone above the last. Notice how the spacing between fret wires shrinks dramatically as you climb — by fret 24 each fret is less than a third the width of the first fret. The math is the same as the 12-tone equal temperament that underlies all Western music since the 18th century.

The math: why frets get closer as you climb

Music is logarithmic. Each octave doubles the frequency — A4 is 440 Hz, A5 is 880 Hz, A6 is 1760 Hz. To divide an octave into 12 equal-sounding semitones (the system called 12-tone equal temperament, standardised in Western music in the 18th century), the frequency ratio between adjacent semitones is the 12th root of 2, approximately 1.05946.

On a vibrating string, halving the length doubles the frequency — so to raise a string's pitch by one semitone, you shorten its vibrating length by a factor of 1.05946. Subtracted from 1, that means each fret position is 5.613% of the remaining string length from the previous one. Or, expressed as a fraction of the original scale length, fret position n from the nut is:

For a Fender 25.5-inch scale length, fret 1 sits 1.43 inches from the nut. Fret 12 sits at 12.75 inches — exactly half the scale. Fret 24 sits at 19.125 inches — three-quarters of the way. The remaining quarter-inch of string between fret 24 and the bridge is enough to keep the tone clean, but only just.

This formula was first worked out properly by the Renaissance lutenist Vincenzo Galilei (1520–1591, the father of the astronomer Galileo), who derived an approximation called the "Rule of 18" — divide the remaining string into 18 parts and the first one is where the next fret goes. The exact value is 17.817, but 18 is close enough that luthiers used the rule for centuries. Modern computer-controlled fret-slotting machines use the exact 12th-root-of-2 calculation.

Why each guitar type chose its own count

Classical guitar — 19 frets. Antonio de Torres's mid-19th-century Spanish design joined the neck to the body at the 12th fret, with a small playable extension over the soundhole reaching the 19th. There is no cutaway in the classical guitar tradition — the body shape is symmetrical, the soundhole is centred, and fret 19 is the limit. Almost no classical repertoire (Bach, Sor, Tárrega, Villa-Lobos) ever asks for higher.

Steel-string acoustic — 20 frets. The early 20th-century Martin Guitar Company added one fret to the classical 19 by extending the fretboard slightly further over the soundhole. Steel-string repertoire (folk, country, bluegrass, fingerstyle) very rarely needs the upper register, but the extra fret was a low-cost design choice that became standard for the entire steel-string industry.

Vintage Fender — 21 frets. Leo Fender's original 1950s designs used a 21-fret maple neck, bolted on to the solid body, with the body itself shaped to allow access via the cutaway. The choice was practical rather than musical — 21 frets fit neatly on the bolt-on neck without requiring a fretboard extension over the body.

Modern electric — 22 frets. Gibson moved to 22 frets in the late 1950s with the introduction of the Les Paul Standard. The 22nd fret on the high E string is D6 — two octaves and a tone above the open E, which is past most rock and blues melodic territory but useful for lead guitarists wanting one more whole step. Fender moved most production to 22 in 1979. Today this is the default.

Shred and metal — 24 frets. Ibanez introduced the 24-fret production electric in the late 1980s, driven by the demands of the technical lead-guitar movement of the time (Steve Vai, Joe Satriani, Yngwie Malmsteen). 24 frets gives exactly two complete octaves on every string — making chromatic scale patterns symmetrical end-to-end — and reaches E6 on the high E string. This is the highest fret count in mainstream production; very rare custom builds extend to 27 or 30 frets, but those are outside normal use.

Typical fret counts by guitar type

Exceptions exist for every row — custom and boutique builds, extended-range 27 and 30-fret experiments, and specialty instruments push the limits in both directions. The numbers above are what you'll find in mainstream production.

The 12th fret — the one with the double dot

If you look at almost any guitar fretboard you'll see small dots inlaid into the wood at certain fret positions — usually frets 3, 5, 7, 9, 12, 15, 17, 19 and 21. They're navigation aids. The 12th fret position is the only one (other than 24, on guitars that have one) marked with two dots stacked vertically. That doubled marker flags the octave point.

At the 12th fret, the vibrating string length is exactly half of what it would be open. Halving a string doubles its frequency, which is the definition of an octave. The note at the 12th fret on the low E string is E3 — exactly one octave above the open low E (E2). Same on every string. Press the 12th fret on the high E and you get E5, one octave above the open high E (E4).

For luthiers and technicians, the 12th fret is also a diagnostic. The pitch of the open string and the pitch of the 12th fret should be exactly the same note one octave apart. If they differ — if the 12th fret reads slightly sharp or flat compared to the open string — that's a setup problem called intonation. It means the bridge saddle is in the wrong position and needs to be adjusted. The guitar tuner can show this directly: tune the open string clean, then play the 12th fret. If it's not also clean, your guitar needs an intonation setup.

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