Metronome

A metronome is a device, mechanical or electronic, that produces a steady audible click at a chosen tempo. The tempo is measured in beats per minute (BPM): how many clicks occur in sixty seconds. A metronome at 60 BPM clicks once per second; at 120 BPM it clicks twice per second (one click every 500 ms); at 240 BPM it clicks four times per second. This page explains how the metronome works, the BPM math, and how to use this online implementation for music practice.

The word "metronome" comes from the Greek metron (measure) and nomos (law), literally "the law of measure." The first widely-adopted mechanical metronome was patented by Dietrich Nikolaus Winkel in Amsterdam in 1814, but it was Johann Nepomuk Maelzel who mass-produced and popularised the device under his own name starting around 1816, which is why Beethoven's tempo markings in his later works (the symphonies from No. 5 onward, the late string quartets) are still marked "M.M." (Maelzel's Metronome) followed by a number.

How to use this metronome

1. Enter your target tempo in the BPM field (30 to 300 BPM). The default is 120 BPM, which is the classical "moderate" tempo used for many walking-pace pieces.
2. Pick a time signature from the dropdown (2/4, 3/4, 4/4, or 6/8). The visual beat indicator below will draw one circle per beat, and beat 1 (the downbeat) will be visually accented.
3. Optionally click the Tap button four times in time with the song you want to match. The metronome will calculate the average BPM from your taps and set the tempo field accordingly. After 3 seconds of inactivity the tap buffer resets so stale taps don't pollute the next measurement.
4. Adjust the volume with the slider (0 to 100%).
5. Choose a subdivision: quarters (one click per beat) or eighths (two clicks per beat, useful for subdivisions in compound metres or for practising inner-voice rhythms).
6. Click Start (or press Space) to begin. Click Stop (or Space again) to halt. The click is synthesised entirely with the Web Audio API, no external audio file is downloaded, no drift accumulates over time, and the audio engine runs at sample-accurate timing.

The formulas

There are two pieces of math behind a metronome, both trivial but worth stating explicitly.

Beat period (seconds per click):

T_seconds = 60 / BPM

At 60 BPM, T = 1 second. At 120 BPM, T = 0.5 seconds. At 240 BPM, T = 0.25 seconds.

Inverse, tempo from a measured interval:

If you measure the time Δt (in seconds) between two consecutive clicks of a steady beat, the BPM is:

BPM = 60 / Δt

Tap-tempo uses this in reverse: you tap N times at the song's pace, the calculator measures the average interval between consecutive taps (Δt), and reports BPM = 60 / Δt.

Tap-tempo averaging across multiple taps:

With N taps, you have (N − 1) intervals. The best estimate of the tempo is:

BPM = 60 × (N − 1) / (t_N − t_1)

where t_1 is the time (in seconds) of the first tap and t_N is the time of the last tap. This formulation is equivalent to averaging the per-interval BPMs and is reliable against jitter on any single tap.

Worked examples

Example 1, A classical Andante (76 BPM)

You're practising the second movement of a concerto marked "Andante." The marking alone is vague, Andante literally means "walking" and historically covers a range from roughly 70 to 90 BPM. You want to settle on a tempo around 76 BPM.

T_seconds = 60 / 76 ≈ 0.789 s per beat

So each beat lasts about 789 ms. Set BPM = 76, choose 4/4, press Start. The first click lands on beat 1, the next 789 ms later on beat 2, and so on. Count "one-two-three-four" in time with the clicks; if your "two" lands on the click that follows "one," you are tracking the metronome. If it consistently lands late, you are dragging, slow down or play with the metronome.

Example 2, Tap-tempo from a recording

You're playing along to a recording of a song and want to know its tempo. Hit the Tap button on each downbeat as the song plays. After four taps, the calculator has three intervals; if those intervals averaged 700 ms:

BPM = 60 / 0.7 ≈ 85.7 → rounded and clamped → 86 BPM

The metronome immediately sets itself to 86 BPM. Now practise the song at that tempo.

Example 3, Eighth-note subdivision at a fast tempo

The piece is marked "Allegro" and you want to practise it at 160 BPM with eighth-note subdivisions to feel the off-beats.

T_quarter = 60 / 160 = 0.375 s per quarter T_eighth = 60 / (160 × 2) = 60 / 320 = 0.1875 s per eighth

Switch subdivision to "Eighths." The metronome now plays two clicks per beat, 0.1875 s apart, and the visual indicator still cycles through four circles per bar at 0.375 s per circle. You can use this to lock onto both the quarter-note pulse and the eighth-note off-beats.

Example 4, Compound time, 6/8

A 6/8 piece at "Allegro moderato" (say 100 BPM, meaning dotted-quarter = 100, the convention for compound metres):

Each of the 6 eighth-note pulses per bar lasts: T_eighth = 60 / 100 ÷ 3 ≈ 0.2 s

Pick 6/8 and quarters, the metronome plays 6 clicks per bar, 200 ms apart, with click 1 accented (higher pitch, darker colour). Practise the two-beat feel: pulses 1-2-3 form the first half of the bar, pulses 4-5-6 form the second half. The visual indicator helps you see where you are inside the bar.

Example 5, Detecting drift

The most valuable use of a metronome is hearing your own drift. Play a scale of C major at 80 BPM for one minute, recording yourself. Then play it again with the metronome. The difference between the two recordings is your drift, the human ear is much worse at detecting tempo drift than at detecting pitch drift, and studies of ensemble performance have shown even professional musicians drift by 5 to 10 ms per beat when playing without a reference. With a sample-accurate digital metronome, you can hear exactly where you're pushing or laying back.

Where a metronome shows up

Metronomes appear across music education, performance, recording, and rehabilitation:

• Instrumental practice. The single most common use. A metronome keeps you honest during slow, deliberate practice, you can't "cheat" a long note by holding it longer than the beat allows. It's also the only way to verify that a fast passage is actually even; many players believe they are playing evenly when their internal clock is wandering.
• Ensemble rehearsal. Conductors use a metronome to lock in a starting tempo for a piece, to verify that tempo changes (accelerando, ritardando) happen at the same rate across the ensemble, and to drill tricky transitions back into tempo.
• Studio recording. A click track (often pre-recorded as part of the session) is the metronome track the drummer or click player follows. Producers use it to edit, overdub, and quantise other parts. Many film and TV composers write to a click because the cue has to match the picture's duration.
• Dance, fitness, and exercise. Boxers, runners, swimmers, and rowers use metronome-style pacing apps (often at 180 BPM for running cadence, the rate most efficient for adult stride frequency).
• Speech therapy and stuttering treatment. Pacing boards and metronome-cued speech are evidence-based techniques for fluency shaping.
• Medical and rehab. Constraint-induced movement therapy and Parkinson's gait training use rhythmic auditory stimulation (RAS), a metronome-driven cue, to improve stride length and symmetry.

Common mistakes

• Setting the tempo to the wrong reference note. In compound time (6/8, 9/8, 12/8), the marking "♩. = 100" means dotted-quarter = 100, not eighth-note = 100. A metronome that defaults to quarter-note clicks would be playing six times faster than the marking intends. Most digital metronomes let you choose the beat unit; ours treats the BPM as the unit you set, so for a 6/8 piece at dotted-quarter = 100, enter 100 BPM and listen to the click as your dotted-quarter pulse, not as one of the six eighth notes.
• Trusting your internal clock. Even experienced players drift. Run a metronome alongside your playing for at least one minute before declaring a tempo "obvious."
• Subdivision confusion. Switching from quarters to eighths doubles the audio rate but doesn't change the time-signature feel. The visual beat circles still cycle through N per bar where N is the time signature numerator, they just highlight the downbeat less often if you're counting the eighths. If you lose track of the bar, switch back to quarters, find beat 1 again, then re-enable eighths.
• Tapping for tap-tempo inconsistently. Tap-tempo assumes your taps are on the beats. If you tap the first two beats and then a pickup note halfway between, the average will be biased and the calculated BPM will be wrong. Reset the buffer by waiting 3 seconds, then tap four clean downbeats.
• Volume too low to hear, too high to track. A metronome click that's too quiet gets masked by your playing; one that's too loud overwhelms your articulation. Set volume so the click is just behind your playing in the mix, you should be able to feel it without flinching.
• Stopping the metronome between repetitions. The most useful habit is to keep the metronome running between takes. The pause between your repetitions is itself a thing you can practise, start your next note exactly on the next click, not "whenever you feel ready."

Frequently Asked Questions

What does BPM mean? BPM stands for "beats per minute", the number of clicks (or beats) in 60 seconds. Higher BPM means a faster tempo. 60 BPM is one click per second; 120 BPM is two clicks per second; 180 BPM is three clicks per second. BPM is a unit of musical tempo, distinct from the absolute length of any particular note value in a piece.

How do I find the BPM of a song I want to practise to? Use the Tap button. Tap four times on the downbeats of the song as it plays. The metronome calculates the average interval between your taps and updates the BPM field. After 3 seconds of no taps, the buffer resets. For best accuracy, tap on a consistent beat (the downbeat) rather than on random strong notes, the more stable your taps, the more accurate the reading.

What's the difference between a time signature and a tempo? Tempo (BPM) is how fast the music goes. Time signature (2/4, 3/4, 4/4, 6/8, etc.) is how the beats are grouped. 4/4 means four beats per bar; 3/4 (a waltz) means three; 6/8 means six eighth-note pulses per bar but felt as two compound beats (1-2-3, 4-5-6). The metronome's beat circles correspond to the top number of the time signature, four circles in 4/4, six in 6/8, and beat 1 is always accented.

Why does the metronome accent beat 1 differently? The first beat of each bar (the downbeat) is the strongest in almost all Western music from the common-practice era onward. Accenting it helps you stay oriented within the bar, you always know where beat 1 is, and from there you can count to any later beat. The visual cue (a darker colour for circle 1) and the audio cue (a higher-pitched 1500 Hz click instead of the standard 1000 Hz) reinforce each other.

Is 120 BPM a good default? 120 BPM is a useful default for two reasons. First, it is the classical "moderate" tempo, sitting comfortably in the range used for walking, moderate marches, and many vocal and instrumental pieces. Second, at 120 BPM each beat is exactly 500 ms long, half a second, which makes it easy to mentally subdivide into half-notes (1 s apart) or eighth-notes (250 ms apart). For most practice purposes, 120 BPM is a reasonable starting point; you can speed up or slow down from there.

Why are there sometimes two clicks per beat (eighths)? Switching subdivision to eighths doubles the click rate. This is useful when a piece has prominent off-beat rhythms, for example, many jazz standards use a swung-eighth feel, and many baroque pieces have running sixteenth notes. Practising with an eighth-note (or sixteenth-note) click underneath helps you lock the off-beats against the main pulse. The visual beat circles still highlight the time-signature beats, so you can keep your place in the bar even when the audio is at twice the rate.

What is the highest BPM the metronome can play? This implementation accepts BPM values from 30 to 300. At 300 BPM, the beat period is 60 / 300 = 200 ms (or 100 ms in eighth-note subdivision). That is at the upper limit of what most humans can perceive as discrete clicks, above 600 BPM individual clicks start to merge into a perceived drone. For most musical purposes, 240 BPM is the practical ceiling.

Why doesn't the metronome play any sound when I press Start? Most often, the cause is that the browser requires a user gesture before audio will play, Chrome, Safari, and Firefox all suspend AudioContexts until you interact with the page. Pressing Start counts as the user gesture; if you've been pressing Start and getting silence, try clicking anywhere on the page first (even on the BPM field), then Start. If that doesn't help, check the tab's audio icon, some browsers show a muted-tab indicator if the tab is muted, and the metronome audio will inherit that.

Is this metronome accurate enough for recording? Yes. The audio engine uses the Web Audio API with the look-ahead scheduling pattern (25 ms scheduler tick, 100 ms schedule-ahead window) that produces sample-accurate timing in modern browsers. The click is synthesised from a square-wave oscillator with a percussive envelope and is therefore independent of any audio-file-loading latency. For professional studio work, you would record the click track once into the session and reuse it; this tool is suitable for both practice and for generating a quick scratch click track to import into a DAW.

How is the BPM range 30 to 300 chosen? 30 BPM is roughly the slowest tempo used in any published music (organ chorale preludes, some adagios). 300 BPM is at the upper edge of human perception and covers the fastest practical tempos (some études, tremolo passages, very fast marches). Values outside this range are musically unusual and tend to be either misreadings of the marking (e.g. M.M. ♩ = 60 is quarter-note = 60, not eighth-note = 60) or transcription errors.

Can the metronome keep going if I switch tabs? Yes, as long as the tab stays loaded. Modern browsers throttle background tabs but do not stop audio playback; the click will continue at the correct tempo. If the browser suspends the tab aggressively (low-power mode, mobile battery saver), you may notice small jitter on resume, but the click will not drift relative to wall-clock time once the tab is foregrounded again.

References

• Maelzel, J. N. (1815). Description of the metronome, or time-keeper. Mechanic's Magazine. (Reprinted in various historical collections; the original patent specification is in the UK National Archives.)
• Wilson, C. (2013). A Tale of Two Clocks, Scheduling Web Audio with Precision. Web Audio API working draft notes. The look-ahead scheduling pattern used by this tool is the one Wilson describes.
• W3C (2023). Web Audio API Specification. W3C Working Draft. Defines AudioContext, OscillatorNode, GainNode, and the timing semantics that make sample-accurate scheduling possible.
• Repp, B. H. (2005). Sensorimotor synchronization: A review of the tapping literature. Psychonomic Bulletin & Review, 12(6), 969 to 992. Covers the empirical literature on human tempo perception and the limits of internal timing.
• Thaut, M. H. (2005). Rhythm, Music, and the Brain. Routledge. Foundational text on rhythmic auditory stimulation in clinical and rehabilitation contexts.