What is a playback speed ratio?

It is the factor by which you speed up or slow down a player. A ratio of 1.25 means 25% faster; 0.8 means 20% slower. Multiply the original BPM by this ratio to confirm you land on the target BPM.

Will pitch change when I alter playback speed?

In a basic speed change (without pitch correction) yes — faster playback raises pitch. Most DAWs and DJ software offer independent time-stretch and pitch-shift so you can change tempo without affecting key.

How far can I time-stretch audio without artifacts?

There is no universal safe percentage. Results depend on the algorithm, source material, settings, and size of the change. Preview the processed audio in your editor, especially after large tempo changes.

How do I find the BPM of a song?

Tap a beat counter (including tools on this site), use a DAW's beat-detection feature, or check a database such as Tunebat or Songbpm.com. Most modern DJ software auto-detects BPM on import.

Does this tool process my audio file?

No. All calculations are pure math performed in your browser. No audio is uploaded or modified — you apply the resulting ratio in your DAW or media player.

Why is my new duration longer when I lower the BPM?

Slowing down a track stretches it in time. If the speed ratio is less than 1 (target BPM original duration.

BPM Tempo Change Calculator

Enter an original and target BPM to calculate the signed speed change, exact ratio, repitch shift, and new duration. No audio is uploaded or processed.

Tempo Settings

Calculation only — this page does not upload, edit, or export audio.

Original BPM

Target BPM

Track Duration (optional)

Leave blank to skip duration calculation.

Enter BPM values and click Calculate to see results.

Speed Ratio

—

× playback speed

Speed Change

—

from original BPM

Repitch Shift

—

key lock off

Tempo Reference Table

Based on original BPM

Speed	BPM	Change	Duration	Semitones

Method, scope, and privacy

Ratio and duration use direct BPM arithmetic. Repitch is an estimate for coupled speed-and-pitch playback; tempo-only processing can preserve pitch. Audio quality after processing depends on the editor and material, so no universal artifact-free range is claimed.

All values are calculated locally in your browser. No audio or entered value is uploaded by this calculator.

Reference: Audacity Change Speed and Pitch manual and Audacity Speed Changer guide.

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Summary

Enter an original and target BPM to calculate the signed speed change, exact ratio, repitch shift, and new duration. No audio is uploaded or processed.

How it works

Enter the original BPM of your track in the first field.
Enter the target BPM you want to reach.
Optionally enter a track duration as whole minutes and seconds from 0 to 59.
Speed ratio = Target BPM ÷ Original BPM; speed change = (ratio − 1) × 100%.
New duration = Original Duration ÷ Speed Ratio; the duration delta shows time added or removed.
The repitch estimate uses 12 × log₂(ratio) semitones and applies only when key lock or pitch correction is off.

Use cases

DJs matching a track to the set BPM before mixing.
Producers time-stretching stems to a project tempo.
Dance instructors finding a safe stretch percentage for class choreography.
Runners calculating what BPM a playlist will hit at a given speed bump.
Music students analyzing how tempo shift affects feel and groove.
Podcasters adjusting speech-rate audio files to target durations.
Fitness coaches syncing workout music to target heart-rate cadence.
Game developers tuning adaptive music loops to match scene pacing.

Frequently Asked Questions

Last updated: 2026-09-22 · Reviewed by Nham Vu