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Tempo Change Calculator
See exactly what a tempo change does to a track: the percent speed change, the pitch shift in semitones and cents if the pitch is not time-stretched, the new key and the new song length. Start from a target BPM, a percentage or a number of semitones.
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Change by
BPM
BPM
%
Negative to slow down, e.g. −8
semitones
Negative to go down; decimals allowed.
Enter your values to see the result.
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How to use the Tempo Change Calculator
- Enter the original tempo of the track in BPM.
- Choose how to change it: target BPM, percent or semitones.
- Add the song length and key if you want the new length and key.
- Read the speed change, pitch shift and new tempo.
- Use the tables to find tempos that land exactly on a semitone.
Tempo change formulas
- Speed ratio r = new BPM ÷ old BPM
- Percent change = (r − 1) × 100
- Semitones = 12 × log₂(r) · cents = 1200 × log₂(r)
- New length = old length ÷ r
- From semitones back to BPM: new BPM = old BPM × 2^(semitones ÷ 12)
Example: 120 → 128 BPM gives r = 1.06667, +6.67%, 12 × log₂(1.06667) = +1.12 semitones (+112 cents), and a 3:30 song becomes 3:16.9.
Semitones vs speed
| Semitones | Speed ratio | Percent | 120 BPM becomes |
|---|---|---|---|
| −3 | 0.8409 | −15.91% | 100.91 |
| −2 | 0.8909 | −10.91% | 106.91 |
| −1 | 0.9439 | −5.61% | 113.26 |
| +1 | 1.0595 | +5.95% | 127.14 |
| +2 | 1.1225 | +12.25% | 134.70 |
| +3 | 1.1892 | +18.92% | 142.70 |
| +12 | 2.0000 | +100% | 240.00 |
A vinyl record recorded at 33⅓ rpm and played at 45 rpm runs 35% fast, about +5.2 semitones; 45 rpm played at 33⅓ is 25.9% slow, about −5.2 semitones.
Tips for DJs and producers
- Harmonic mixing: without key lock, a change of about ±6% moves a track a full semitone, which can push it out of key with the next track.
- Small changes are safe: under about ±3% (roughly half a semitone) most listeners do not notice the pitch change.
- Use time-stretch for big jumps: for changes above roughly 10%, stretching artifacts or obvious pitch changes become audible; picking a track closer in tempo often sounds better.
Frequently asked questions
How do I convert a BPM change to a percentage?
Divide the new tempo by the old one, subtract 1 and multiply by 100. From 120 to 128 BPM: 128 ÷ 120 = 1.0667, so the track plays 6.67% faster.
How many semitones is a tempo change?
If pitch follows speed, semitones = 12 × log₂(new BPM ÷ old BPM). For 120 → 128 BPM that is 12 × log₂(1.0667) = 1.12 semitones, or about 112 cents higher.
How much faster is one semitone?
One semitone up is a speed ratio of 2^(1/12) = 1.0595, about 5.95% faster. Two semitones is 12.25% faster, and an octave (12 semitones) is exactly double speed.
Does changing the tempo always change the pitch?
Only without time-stretching. Turntables, tape machines and simple resampling raise the pitch along with the speed. DJ software with key lock (master tempo) and DAW time-stretch keep the original pitch while changing the tempo.
How does a tempo change affect song length?
Length is divided by the speed ratio. A 3:30 song (210 s) sped from 120 to 128 BPM lasts 210 ÷ 1.0667 = 196.9 s, or 3:16.9.
What is the range of a DJ pitch fader?
Many turntables and DJ controllers offer ±8% by default, with wider ±16% or more as an option. A change from 120 to 128 BPM (+6.67%) fits within ±8%.
Are all the tools on FreeToolCabin tested for quality and accuracy?
Yes! Every tool on our site undergoes automated Q/A testing in real browser environments to ensure high precision, correct output, and zero errors. If you happen to spot a bug or have a suggestion, please contact us at [email protected] and our team will review it right away.
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