Capo Key Transpose Calculator
A capo lets you keep familiar open-chord shapes while shifting the whole song to a higher key. Because each fret is one semitone, the sounding key is simply the shape key transposed up by the capo fret number. Choose the key of the chord shapes you are playing and the fret your capo is on, and this calculator shows the actual sounding key, how many semitones higher it is, and the new tonic frequency from a tuning reference you set.
Capo transpose formula
sounding pitch class = (shape key + capo fret) mod 12
semitones up = capo fret
new frequency = reference * 2^(capo fret / 12)
cents = capo fret * 100
The pitch classes are numbered C = 0 up to B = 11. Adding the capo fret and taking the result modulo 12 wraps around the octave to name the new key.
Capo examples
- G shapes, capo 2: sounds in A.
- C shapes, capo 3: sounds in E flat (D#).
- E shapes, capo 4: sounds in G#.
- D shapes, capo 5: sounds in G.
- Capo 0 means no transposition: the sounding key equals the shape key.
Capo transposition: frequently asked questions
How does a capo change the key?
A capo clamps all the strings at a chosen fret, shortening every string by the same amount. Each fret raises the pitch by one semitone, so a capo on fret 3 raises everything by 3 semitones. If you play chord shapes from the key of C with a capo on fret 3, the music sounds in E flat.
How do I keep the same shapes but match a singer?
Decide the key the singer needs (the sounding key) and the easy shapes you want to play. The capo fret is the difference in semitones between the two. If you play G shapes and need the song to sound in A, place the capo on fret 2, because A is 2 semitones above G.
Does a capo transpose up or down?
Always up. A capo can only shorten the strings, raising the pitch. To sound a key lower than your open shapes, you either retune down or choose different chord shapes; a capo alone cannot lower the key.
What does the new tonic frequency tell me?
It shows the equal-tempered frequency of the new key note after transposition, based on a reference you enter. This is handy for tuning, matching backing tracks, or checking the pitch against a tuner.
Sources and definitions
- Capo transposition is exact semitone shifting: each fret is one equal-tempered semitone, frequency multiplied by the twelfth root of 2. This is a standard music-theory definition.
- National Institute of Standards and Technology: SI units reference (frequency in hertz).
Reviewed by the CalculatorHub team, edited by James Graham, 19 June 2026. See our methodology.