BPM Math
Free music and audio tools with the maths shown: a tap tempo BPM counter, BPM to milliseconds for every note value, delay and reverb times by tempo, note to frequency and back, a key and chord transposer, and song length in bars.
The numbers behind a session, without the app-store detour: tap a tempo, get every delay time on the grid, set a reverb that fits the bar, count bars into minutes, find a note's frequency, move a song to a singer's key. Each tool shows the formula and a reference table.
Tempo and timing covers BPM, milliseconds, delay, reverb and song length. Pitch and key covers frequencies, MIDI numbers, cents and transposition.
Tempo & timing
Tap along to any song with a key or click and get its tempo in BPM, averaged over your taps, with the beat length in milliseconds and the nearest common tempo.
BPM → millisecondsMilliseconds and Hz for every note value at your tempo: whole to 64th notes, dotted and triplet, so delay times, LFO rates and sidechain releases sit on the grid.
Delay & reverb timesTempo-synced reverb pre-delay and decay times for tight, room, hall and plate settings, and delay times for every note division, from your song's BPM.
Bars ↔ minutesHow long a song, section or loop runs from its bars, BPM and time signature, and how many bars fit a target length, with a bars-per-minute table.
Pitch & key
Convert any note to its frequency in Hz and any frequency to the nearest note with the cents offset, plus the full A4 = 440 Hz chart and MIDI numbers.
Key & chord transposerMove a key or a whole chord progression up or down by semitones, or between concert pitch and B♭, E♭ and F instruments, with the new chords written out.
Frequently Asked Questions
Where do the formulas come from?
They are the standard ones: 60,000 ÷ BPM for the length of a beat, twelve-tone equal temperament at A4 = 440 Hz for pitch, 1,200 cents to the octave, and MIDI note numbering. The reverb and delay conventions are the producer rules of thumb, and the pages say so. Every tool shows its arithmetic and a table so you can check it.
Does the BPM counter listen to my music?
No. It times your taps on a key or the screen and averages them, which is the same method as the tap-tempo button in a DAW. Tap steadily for eight or more beats and the reading settles to within a BPM. Nothing is recorded or uploaded.
Do I need an account, and is anything saved?
No account, nothing saved. Every calculation runs in your browser and nothing you type or tap is sent anywhere.