Transpose Calculator
Transposition moves all notes in a piece of music by the same interval, changing the key without altering the relationships between notes. This is essential when adapting music for instruments in different keys (such as Bb trumpet or Eb alto saxophone), fitting a singer's vocal range, or experimenting with different key signatures. Select a starting note and the number of semitones to transpose (positive for up, negative for down), and the resulting note name is shown immediately.
Transposition formula
Result = (start_semitone + transpose) mod 12
Notes: C=0, C#=1, D=2, D#=3, E=4, F=5,
F#=6, G=7, G#=8, A=9, A#=10, B=11
Modular arithmetic wraps around at 12, so going up from B (11) by 2 gives C# (1). Going down from C (0) by 3 gives A (9). The octave does not change the note name, so the calculator shows the pitch class (note name without octave number).
Common transposition intervals
- +1 semitone: minor second (half step) - raises key by one step.
- +2 semitones: major second (whole step) - used for Bb instruments.
- +3 semitones: minor third.
- +4 semitones: major third.
- +5 semitones: perfect fourth - very common transposition.
- +7 semitones: perfect fifth.
- +9 semitones: major sixth. Equivalent to -3 semitones going down.
- +12 semitones: octave - returns to same note name.
Transposition: frequently asked questions
What does transposing by semitones mean?
Transposing by semitones moves every note in a piece by the same fixed interval. Moving up 1 semitone raises the pitch by one half-step (e.g., C becomes C#). Moving down 2 semitones lowers by a whole step (e.g., A becomes G).
How do I transpose up a perfect fourth?
A perfect fourth is 5 semitones. Enter your starting note and set transposition to +5. For example, C transposed up 5 becomes F.
How do I transpose for a Bb instrument?
Instruments like the trumpet or clarinet in Bb sound a major second (2 semitones) lower than written. To convert written music to concert pitch, transpose down 2 semitones. To write for a Bb instrument from concert pitch, transpose up 2 semitones.
What is the range of transposition?
Since there are 12 semitones in an octave, any transposition of +12 or -12 semitones brings you back to the same note name (one octave higher or lower). Transpositions are modular arithmetic on the 12-note chromatic scale.
How does this calculator handle sharps and flats?
The calculator shows the result using sharps (C#, D#, F#, G#, A#) by default, which matches the chromatic scale convention. Enharmonic equivalents (Db = C#, Eb = D#, etc.) are the same pitch; use whichever fits your key signature.
Official sources
- MIDI Association: midi.org - MIDI note and transposition specifications.
- Audio Engineering Society (AES): aes.org - music theory and audio standards.
Reviewed by the CalculatorHub team, edited by James Graham, 15 June 2026. See our methodology.