Semitone Frequency Transpose Calculator
Enter a starting frequency and how many semitones to shift it. The calculator returns the transposed frequency in hertz and the pitch ratio, using equal temperament where each semitone is the twelfth root of two.
How to use the semitone calculator
- Enter the starting frequency in hertz, for example 440 for A4.
- Enter how many semitones to move, positive for up or negative for down.
- Read the transposed frequency and the pitch ratio between the two notes.
Examples
Up an octave
440 Hz, +12 semitones
880 Hz (ratio 2)
Up a perfect fifth
440 Hz, +7 semitones
659.26 Hz (ratio 1.4983)
Frequently asked questions
How does the semitone calculator work?
It multiplies the starting frequency by the pitch ratio 2^(semitones / 12). In equal temperament each semitone is the twelfth root of two, so twelve semitones double the frequency.
What is the ratio for one semitone?
One semitone has a ratio of 2^(1/12), about 1.059463. Shifting up by a semitone multiplies the frequency by that value, and shifting down divides by it.
Can I transpose downward?
Yes. Enter a negative number of semitones. Moving down twelve semitones gives a ratio of 0.5, so 440 Hz becomes 220 Hz one octave lower.
Why is a perfect fifth not exactly 1.5?
In equal temperament a fifth is seven semitones, a ratio of about 1.4983, slightly narrower than the 1.5 of just intonation. The small difference keeps every key in tune.
Does the starting frequency have to be a musical note?
No. Any positive frequency works, so you can transpose a sample, an oscillator pitch or a filter cutoff by a musical interval.
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