BPM calculator
At 120 beats per minute a quarter note is exactly 500 milliseconds and a bar of four is exactly two seconds. Every other tempo is easiest to reason about relative to it. 60 BPM doubles everything, 240 halves it. It is also why so much dance music sits between 120 and 130: the arithmetic is clean and the tempo sits close to a brisk walking pace.
A beat lasts 60,000 divided by the tempo in milliseconds. At 120 BPM a quarter note is 500 ms, an eighth 250 ms, a dotted quarter 750 ms and a quarter triplet 333.33 ms, and a bar of four takes exactly two seconds. The dotted and triplet rows follow whichever note you pick, so choosing an eighth turns them into 375 and 166.67. The same page runs the sum backwards, in bars, and in semitones of pitch.
How to work out tempo timings
Tempo-synced delay is the difference between an effect that sits in a track and one that fights it. A delay set to an arbitrary 380 ms against a 120 BPM song produces repeats that drift across the beat and muddy everything; the same delay at 375 ms locks to a dotted eighth and reads as part of the arrangement. Most plugins now offer host sync and do this for you, which is exactly when knowing the underlying numbers stops being necessary and starts being useful; for hardware, for guitar pedals, and for understanding why a preset does not fit.
Why the dotted eighth is the one everyone uses
A dotted eighth is three sixteenths long, so its repeats land between the quarter notes rather than on them. That fills the space without reinforcing the pulse, which is why a plain quarter-note delay so often sounds like it is competing with the drums while the dotted eighth sounds like part of the arrangement. At 110 BPM it is 409 ms, at 120 it is 375. Reverb uses the same table from the other end: a sixteenth of pre-delay keeps the dry signal clear before the tail arrives, and a decay of about one bar means the tail has cleared by the time the next bar starts.
Working backwards, and the factor-of-two trap
Measuring a loop and converting back to a tempo is the same equation inverted, and it is where the arithmetic earns its keep. A 500 ms region is 120 BPM if it is a quarter note and 240 if it is an eighth, which is why the reading comes with its half-time and double-time neighbours: a tempo that looks wrong by a factor of two almost always is. It is the same relationship that makes drum and bass at 174 and hip-hop at 87 feel related instead of unrelated.
Below the millisecond level the unit that matters is samples. At 44.1 kHz one millisecond is 44.1 samples, so a 500 ms beat is exactly 22,050, which is why 120 BPM loops slice cleanly at that rate and awkward tempos do not. A loop cut a few samples short accumulates drift over repeats, heard as a gradual slide against the grid instead of an obvious error.
Semitones, for when the tempo tab is not the answer
Pitch runs on the same kind of arithmetic and belongs beside it. Each semitone multiplies frequency by the twelfth root of two, about 1.05946, so twelve of them double it exactly. The reference itself is a convention that has moved: A440 was only agreed internationally in 1955, baroque ensembles commonly play at 415 a full semitone lower, and some orchestras tune to 442 for a brighter sound. The 432 Hz tuning that circulates online has no historical or acoustic basis, but it is a valid reference like any other and the field accepts it.
What people use it for
- Setting a delay pedal or plugin to the track tempo
- Timing reverb pre-delay and decay to the track
- Working out how long an eight-bar section runs
- Getting the tempo back from a measured loop length
- Checking whether a tempo reading is half or double time
- Trimming a loop to an exact number of samples
- Tuning to a non-standard reference such as 415 or 432 Hz
- Finding the frequency of a note for a notch filter
Questions
Divide 60,000 by the tempo. At 120 BPM that is 500 ms per quarter note, and 468.75 ms at 128 BPM.
Divide 60,000 by the millisecond length of a quarter note. Use the Milliseconds to tempo tab and say which note value you measured.
Tapping has its own page: the BPM tapper takes the beat from your finger and hands back a tempo you can bring here. For an exact figure, loop a bar in your editor, read its length in milliseconds and use the Milliseconds to tempo tab; a measured loop settles the question, and a tapped one only narrows it.
A dotted eighth for a rhythmic slapback, a quarter for something obvious, a sixteenth for thickening. All three are listed above.
One and a half times the note length. A dotted eighth at 120 BPM is 375 ms, and at 110 BPM it is 409 ms.
Three notes in the space of two, so two thirds of the length. A quarter triplet at 120 BPM is 333 ms.
The gap between the dry sound and the start of the reverb. A sixteenth note keeps the source clear before the tail arrives.
About one bar for most material, so the tail clears before the next bar starts.
Beats per bar times the beat length. Four beats at 120 BPM is exactly two seconds, so thirty bars fill a minute.
Fifteen at 120 BPM in 4/4. At 128 BPM it is exactly sixteen, because a bar is 1.875 seconds.
Yes. A bar of 3/4 at the same tempo is three quarters the length of a bar of 4/4, so set the beats per bar instead of assuming four.
You have probably measured a hi-hat and not the beat. Check the half-time row; it is usually the answer.
At 44.1 kHz, the millisecond length times 44.1. A 500 ms beat is exactly 22,050 samples.
It has been cut a few samples short or long. Over many repeats the error accumulates against the grid.
Reference × 2^(semitones ÷ 12). Twelve semitones doubles the frequency, which is the octave.
A hundredth of a semitone. The smallest pitch difference most people can hear is around five to ten cents.
There is no acoustic or historical evidence for the claims made about it. It is simply a different reference, and the field accepts it.
No. Every figure assumes one constant tempo, so a track with a tempo map has to be added up section by section.