Tempo Change
Half time, double time, and percentage shifts — with what each one does to the beat length you are working to.
Beats per minute, 20 to 400.
Negative slows down, positive speeds up.
Beat length moves from 500 ms to 500 ms.
That result falls outside 20–400 BPM.
- Per beat
- ms
- Per bar (4/4)
- ms
- Frequency
- Hz
- 1/8 delay
- ms
Half time and double time keep the same grid while changing the perceived pace: 174 BPM drum and bass is felt at 87. A percentage change scales the tempo directly, so +8% of 120 BPM is 129.6. Both views are below, with the resulting beat length for each.
Half time and double time
These do not change the grid. They change which layer of the rhythm you count as the beat, which is why the same track has two defensible BPM values.
| Feel | Tempo | Beat length | Notes |
|---|---|---|---|
| Quarter time | 30 BPM | 2000 ms | Rarely used outside ambient and drone. |
| Half time | 60 BPM | 1000 ms | Same grid, half the perceived pace. The usual cause of a halved BPM reading. |
| Current | 120 BPM | 500 ms | The tempo as entered. |
| Double time | 240 BPM | 250 ms | Same grid, twice the perceived pace. |
| Quadruple time | 480 BPM | — | Only meaningful at very slow source tempos. |
Values outside 20–400 BPM are shown as a dash rather than a number the tools cannot work with.
Percentage change versus feel change
These are two different operations and confusing them causes real problems.
A percentage change genuinely alters the tempo. Playing a 120 BPM track at +8% makes it 129.6 BPM, everything happens sooner, and if speed and pitch are coupled the whole thing rises by about a semitone. The pitch calculator covers that side.
A feel change alters nothing about the audio. Calling a 174 BPM drum and bass track "87 BPM half time" describes the same recording, played at the same speed, counted differently. Nothing is faster or slower, and the pitch is untouched.
Where this matters in practice
- Beatmatching. Percentage is the operation. A turntable or DJ deck gives you a percentage fader, and the pitch moves with it.
- Reading a BPM tag. Feel is the ambiguity. A tag of 87 on a drum and bass track means half time, not a slow track.
- Setting delays. Feel changes nothing. A delay at 174 BPM and a delay at "87 BPM half time" are the same delay — but if you type 87 into a calculator you will get double the time you wanted.
The practical test. If the audio sounds different after the change, it was a percentage change. If only your counting changed, it was a feel change.
Need every value at once?
The main BPM calculator shows milliseconds, delay times, reverb ranges, hertz and bar length together, updating from a single tempo.
Half time and double time explained
Why the same track has two correct BPM values, and how to tell which one a genre expects.
Common questions
What is the difference between half time and halving the tempo?
Half time changes nothing about the audio, only how you count it. Halving the tempo genuinely slows the playback and, with speed and pitch coupled, drops the pitch by an octave.
Which BPM should I type into a delay calculator?
The tempo your DAW project is set to, always. If a drum and bass project runs at 174, use 174 even if the track feels like 87. Using the felt tempo doubles every delay time.
What does +8% do to a tempo?
It multiplies it by 1.08. A 120 BPM track becomes 129.6 BPM. That is the standard turntable pitch range, and it also raises the pitch by a little over one semitone.
Related tools and guides
- BPM and Pitch Calculator See what a tempo change does to pitch. Converts between two tempos, a percentage shift and semitones or cents, for turntables and samplers. Converter
- Tempo Ranges by Genre Typical BPM ranges for common genres, with the overlaps and half-time ambiguities that trip up tempo detection, and what each range means in ms. Reference
- BPM Calculator Tap a tempo and get every value it drives: milliseconds per beat, delay and reverb times, hertz, frames and bar length. Free, instant, no sign-up.
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