Varispeed calculator

Pitch shift and tempo

Calculate the frequency ratio, speed change and resulting BPM when varispeed shifts audio pitch up or down by semitones.

Pitch & tempo: settings and guide

Original tempo

BPM

Pitch change

semitones

Varispeed tempo134.695 BPM+12.246% speed · 1.122462× ratio

Frequency ratio1.122462×

Speed change+12.246%

Inverse speed change−10.910%

Pitch change+200 cents

This relationship applies when pitch and speed are linked. Pitch-preserving processing can change one without changing the other.

Formula

How pitch and tempo change with varispeed

An octave contains 12 semitones. For a shift of s semitones, the speed ratio is 2^(s ÷ 12). In varispeed playback, pitch, playback speed and BPM all change by that same ratio.

speed ratio = 2 ^ (semitones ÷ 12)

01
A positive semitone shift raises pitch and speeds up linked varispeed playback.
02
A negative semitone shift lowers pitch and slows down the tempo.
03
Time stretch that preserves pitch changes tempo separately. It does not follow this linked varispeed rule.

Worked example

Example: shifting 120 BPM by one octave

Raising linked varispeed by 12 semitones gives a ratio of 2, so 120 BPM becomes 240 BPM. Lowering it by 12 semitones gives a ratio of 0.5, so 120 BPM becomes 60 BPM.

Good to know

Assumptions and limits

Pitch and speed are linked, as with tape-style varispeed or resampling.
The calculation uses 12-tone equal temperament.
Pitch-preserving time stretch and formant controls do not follow this relationship.

Review BeatTiming's calculation accuracy, precision and release-testing methodology.

Varispeed reference

Common semitone, speed and BPM changes

Tape-style varispeed ties pitch, playback speed and tempo to the same ratio. Moving upward by a given number of semitones is not the exact percentage inverse of moving downward by that number, so the table calculates each direction separately.

Linked varispeed from a 120 BPM source

Speed ratio, percentage change and resulting BPM for common semitone shifts from 120 BPM
Shift	Speed ratio	Speed change	Resulting BPM
-12 semitones	0.5×	−50.000%	60 BPM
-7 semitones	0.66742×	−33.258%	80.09 BPM
-5 semitones	0.749154×	−25.085%	89.898 BPM
-1 semitones	0.943874×	−5.613%	113.265 BPM
+1 semitones	1.059463×	+5.946%	127.136 BPM
+5 semitones	1.33484×	+33.484%	160.181 BPM
+7 semitones	1.498307×	+49.831%	179.797 BPM
+12 semitones	2×	+100.000%	240 BPM

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Quick answers

Frequently asked questions

What happens when I pitch up one octave?

An octave is 12 semitones, so linked varispeed doubles the speed and BPM.

Why does my pitch shifter not change BPM?

Some pitch shifters keep the audio’s length unchanged. This tool covers varispeed, where pitch and speed change together.

How many percent is one semitone?

One semitone up multiplies pitch and speed by about 1.05946. That is an increase of about 5.946%.