Transpose musical keys, melodies, and chord progressions up or down by any semitone interval. Calculate guitar capo fret positions and transposing instrument intervals instantly.
| Original Note / Chord Root | Transposed Equivalent (+5 semitones) |
|---|
Last updated: October 31, 2026 · Written by the Pitch Detectors Editorial Team
A key transposition calculator shifts any musical key, chord, or melody up or down by semitones — instantly showing the new key, the interval name, guitar capo positions, and concert-pitch equivalents for transposing instruments. Pick a key, choose an interval, done.
Musicians transpose constantly: singers need songs in comfortable vocal ranges, guitarists use capos to keep open-string voicings, and arrangers rewrite parts for transposing instruments like trumpets and saxophones. DJs meet the same idea as pitch shifting — a +5.95% speed change is a one-semitone transposition (see the BPM to Speed Calculator).
Select your original key root and scale mode (major or minor), then enter the semitone shift — positive for up, negative for down — or tap a quick interval button (perfect fourth, perfect fifth, octave). The calculator returns the new key with correct enharmonic spelling, the interval name (e.g. +7 = perfect fifth), the guitar capo fret for the move, and concert-pitch equivalents for B♭, E♭, and F instruments.
Methodology: chromatic index arithmetic mod 12 on the 12-tone equal-temperament circle (C=0 … B=11); enharmonic spelling prefers sharps for upward and flats for downward motion; capo fret = semitones mod 12; transposing-instrument offsets applied from concert pitch. We verified the widget against hand calculations on five sample inputs (G +5 → C; C −4 → A♭; D +7 → A; F♯ −2 → E; B♭ +2 concert for trumpet → C written) — every result matched exactly.
Worked example: transpose G major up 5 semitones:
Need the song's current key first? Find it with the Song Key Finder.
| Readout | Meaning | Next step |
|---|---|---|
| New key | Transposed key, correctly spelled | Rewrite chord charts in the new key |
| Interval name | Musical distance (e.g. perfect fifth) | Communicate the move to other musicians |
| Capo fret | Where to clamp for guitar | Capo there and play original shapes |
| B♭ / E♭ / F parts | Written pitches for transposing instruments | Hand these to horn players directly |
A capo raises pitch — fret 3 makes everything 3 semitones higher. That gives you two opposite superpowers. To play higher: keep your familiar chord shapes and clamp the capo at the transposition fret (G shapes + capo 2 = sounding in A). To stay in the same key with easier shapes: go the other way — want to sound in G but love C shapes? Capo 7 (G is 7 semitones above C) and play C shapes.
The mental shortcut: capo fret + shape key = sounding key (in semitones). Capo 5 + G shapes = C sounding. Rearranged: shape key = sounding key − capo fret. This is how session guitarists survive last-minute key changes — the singer wants it down a whole step, you slide the capo down two frets and change nothing else.
Some instruments are built in other keys: when a B♭ trumpet "plays C," concert pitch hears B♭. To write for them, transpose from concert pitch to their written pitch:
| Instrument | Transposition | Concert C becomes (written) |
|---|---|---|
| Trumpet, clarinet, tenor sax | B♭ (−2 semitones) | D |
| Alto sax, baritone sax | E♭ (−9 semitones) | A |
| French horn | F (−7 semitones) | G |
| Piccolo | Octave up (+12) | C (8va) |
Worked example: the band plays in concert B♭ major and you need a trumpet part. B♭ is index 10; add 2 → 12 mod 12 = 0 = C major written. The trumpeter reads C major and the audience hears B♭ — everyone wins. Reverse it to find concert pitch from a written part: subtract instead.
C♯ and D♭ are the same piano key but different spellings — and correct spelling matters for reading musicians. The rule of thumb: use sharps when transposing up, flats when transposing down, and keep the key signature sane (prefer 3 flats over 9 sharps). Transposing C up 1 semitone gives D♭ in flat-friendly contexts (jazz, brass) but C♯ in sharp-friendly ones (guitar, strings).
The calculator follows this convention automatically, and avoids theoretical keys (no G♯ major with its F𝄪) by respelling to the practical equivalent. If you're writing for specific players, match their instrument's tradition: brass reads flats, strings read sharps.
Transposition moves an entire piece to a new key — everything shifts together. Modulation changes key within a piece, like the classic final-chorus lift up a whole step. DJs do live modulation with pitch faders; producers automate it. The math is identical (semitone shifts); the difference is scope — one moves the song, the other moves a section. For DJ key changes between tracks, see the DJ Transition Calculator.
Session players often skip note names entirely with the Nashville Number System: chords become scale degrees (1, 4, 5, 6m). A I–V–vi–IV progression in G is G–D–Em–C; in C it's C–G–Am–F — same numbers, instant transposition. Learn progressions as numbers once, and you can play them in any key the calculator gives you without rewriting charts. It's transposition as a habit rather than a calculation.
| Method | Speed | Use when |
|---|---|---|
| This calculator | Instant | Any key change, capo positions, horn parts |
| Capo only | Instant (guitar) | Staying in guitar-friendly keys live |
| Nashville numbers | Real-time | Session playing with key changes on the fly |
| DAW transpose | Instant (audio/MIDI) | Production; watch for formant artifacts on audio |
| Manual theory | Slow | Learning; builds the underlying understanding |
Calculate here for correctness, then internalize the patterns — the goal is reaching for the capo or the numbers without thinking.