How song length is worked out
Tempo tells you how many beats pass each minute, and the time signature tells you how many beats are in a bar. Multiply bars by beats per bar to get the total beats, divide by the BPM, and you have the length in minutes. It's handy for planning arrangements, cutting a track to fit a video or ad slot, or checking how long an intro really is.
The one thing to watch is what your BPM counts. In 4/4 and 3/4 it's always the quarter note. In meters like 6/8 it varies: most DAWs keep counting quarter notes by default (a 6/8 bar is three quarter notes long), musicians often feel two dotted-quarter beats per bar, and some charts count every eighth note. Pick the option that matches your tempo.
The formula
beats per bar = bar length ÷ length of the counted beat (quarter = 1, dotted quarter = 1.5, eighth = 0.5)
seconds per bar = beats per bar × 60 ÷ BPM
length (s) = bars × seconds per bar · bars = length (s) ÷ seconds per bar
Example: 64 bars of 4/4 at 120 BPM
| Step | Result |
|---|---|
| Beats per bar | 4 |
| Seconds per bar: 4 × 60 ÷ 120 | 2 s |
| Total beats: 64 × 4 | 256 |
| Total seconds: 64 × 2 | 128 s |
| Length | 2:08 |
Going the other way at the same tempo, a 3:30 target is 210 ÷ 2 = 105 bars.
Tips for arranging to a length
- Think in 4- and 8-bar phrases. If you need 105 bars, an extra bar of silence or a 4-bar tag usually sounds better than an odd phrase.
- Leave room for the tail. Reverb and delay ring past the last bar; allow a second or two before a hard cut.
- Fit to picture by nudging tempo. Small tempo changes of 1 to 2 BPM rarely feel different but can shift the end by several seconds.
- Check DAW settings for compound meters; if the arrangement runs long or short by a factor of 1.5 or 2, the BPM is counting a different note.
Frequently asked questions
How do you calculate the length of a song from BPM?
Multiply the number of bars by the beats in each bar to get the total beats, then divide by the BPM to get minutes. 64 bars of 4/4 at 120 BPM is 256 beats ÷ 120 = 2.13 minutes, or 2:08.
How many bars is a 3 minute song?
It depends on the tempo. In 4/4 at 120 BPM each bar lasts 2 seconds, so 3 minutes is 90 bars. At 100 BPM a bar is 2.4 seconds and 3 minutes is 75 bars. Use the length-to-bars mode for your tempo.
How does BPM work in 6/8 time?
It depends on what the tempo counts. Most DAWs measure tempo in quarter notes by default, so a bar of 6/8 lasts three quarter notes. Musicians often count 6/8 in two dotted-quarter beats per bar, and some scores count every eighth note. Choose the option that matches how your tempo is written; the calculator converts the bar length for you.
How long is a bar of music?
In 4/4, a bar lasts 240 ÷ BPM seconds: 2 seconds at 120 BPM, 2.4 seconds at 100 BPM and 1.6 seconds at 150 BPM. In 3/4 it's three quarters of that.
What length should a song be for radio or streaming?
Most popular songs run about 2:30 to 4:00. Streaming has pushed many songs shorter; Spotify, for example, counts a stream after 30 seconds of listening, however long the track is. Radio edits are often trimmed to under about 3:30.
Rates and figures last checked October 2026.
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