What is the reciprocal line for?

It gives the speed that returns a shifted pitch to where it started, which is the inverse of the percentage you set. Playing a file at a hundred and five percent and then at the reciprocal speed brings it back to its original key, which is the practical way to undo a resample.

Is six percent of speed really a semitone?

Very close to it. The exact figure is the twelfth root of two, which is about five point nine five percent, so six percent is a good mental approximation and the reason a slightly fast tape sounds about a semitone sharp.

Why does speed affect pitch at all?

Because playing a recording at a different rate is resampling it, and resampling compresses or stretches the waveform in time. Every frequency in the signal is multiplied by the same factor, so the whole spectrum moves together and the key changes with the tempo.

How is this different from time stretching?

Time stretching changes duration without resampling, by rebuilding the audio from overlapping grains, so the pitches stay where they are. The two operations have the same effect on duration and opposite effects on pitch, which is why a speed change is only safe when the pitch consequence is acceptable.

Can I use the interval panel to check a tuning?

For an interval between two measured pitches, yes, and the cents figure is the one to read. For a single pitch measured against its intended note, the frequency to MIDI note tool is more direct because it names the note automatically.

Pitch Shift Calculator

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Audio Pitch Shifter

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Playback Speed Calculator

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Cents Calculator

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Musical Transpose Tool

Transpose music to different keys

Pitch Shift Calculator quantifies two things: the interval between any two pitches, and how far a speed change would move one. It is a reference for the arithmetic behind pitch shifting rather than a tool that processes audio.

What is Pitch Shift Calculator?

Use either panel: two frequencies give the interval between them, or a speed percentage gives the pitch shift that resampling at that speed would produce.

The two panels:

An interval panel taking two frequencies and reporting the difference in cents and in semitones, along with the notes each frequency sits nearest to.
A speed panel with a slider from fifty to two hundred percent, reporting the shift in cents, where the base frequency lands afterwards, which note that is nearest, and the reciprocal speed that would return it to where it started.
A note explaining that time stretching changes duration without touching pitch while resampling moves both together, and that the coupling is exactly what the calculator quantifies.

The two panels describe the same relationship from opposite ends, and that is the point of having both. Given two pitches, the interval panel says how far apart they are, taking the logarithm of their ratio and scaling it into cents; a semitone comes out at a hundred and an octave at twelve hundred, which makes any interval legible at a glance. Given a speed, the speed panel says what resampling at that rate would do, which is the calculation behind speeding a record up or down and the reason a slightly fast tape changes the key of what is on it. Speed and pitch are proportional under resampling, so a hundred and five percent speed is about eighty five cents sharp, roughly a semitone, and it is worth remembering as a rule of thumb that about six percent of speed is about one semitone of pitch. The reciprocal line is the practical one: it gives the speed that undoes a change, which is what is needed to return a file to its original pitch after it has been played at a different rate, and it is simply the inverse of the percentage rather than a new calculation. Both panels are pure arithmetic on the figures entered, and no audio passes through the tool at all.

What it does not do:

It processes no audio and produces no files.
It assumes resampling for the speed relationship, so it does not describe time stretching.
No formant or timbre effects of a large shift.
Equal temperament only for the note names.
No handling of a speed that varies over time.
Nothing is uploaded, and no history is kept.

Use it to work out what a speed change would do to a pitch before applying it, to measure the interval between two readings, or to find the speed that returns a file to its original key. When the shift has to be applied to real audio with the pitch and duration decoupled, the audio pitch shifter does that, and when the question is the duration consequence of a speed change rather than the pitch consequence, the playback speed calculator approaches the same relationship from the timing end. Both panels are worth keeping in mind as a single relationship rather than two facts, since the interval between two pitches and the pitch consequence of a speed change are the same logarithm seen from different sides, and a figure in cents is often the quickest way to compare a measured interval against a proposed change.

How to use Pitch Shift Calculator

Enter two frequencies to read the interval between them in cents and semitones.
Or set a speed percentage to read the pitch shift it would produce.
Use the reciprocal figure to find the speed that undoes a change.
Remember that about six percent of speed is about one semitone of pitch.

When to use Pitch Shift Calculator vs related tools

Pitch Shift Calculator is the tool for the arithmetic of pitch and speed relationships, and for checking a change before applying it. Audio Pitch Shifter applies a shift while leaving the duration alone. Playback Speed Calculator covers the timing side of the same relationship, and Cents Calculator works purely in the tuning unit when the interval is small enough that semitones are too coarse.

Privacy & Security

This tool runs entirely in your browser — no data ever leaves your device. There is no server round-trip, no upload, no logging, and no account required. Your input is processed locally using client-side JavaScript and is never stored, transmitted, or accessible to anyone else. When you close the tab, everything disappears.