How this tool works
Tempo tells you how many beats happen in a minute, so one beat always lasts 60 ÷ BPM seconds. A bar is a fixed group of beats set by the time signature — four in 4/4, three in 3/4 — so once you know the tempo, the length of every bar is fixed too. Multiply by the number of bars and you have the duration.
The reverse mode rearranges the same formula. It converts your target length into beats, then into bars:
That exact figure is rarely a whole number, so the tool also lists practical options: rounding down or up to a whole bar, and snapping to the nearest 4-bar or 8-bar phrase, which is how most arrangements are built. For each option it shows how far from your target you would land and the precise tempo that would make that bar count hit the target exactly — handy when you have some freedom over the BPM.
How to use this tool
- Choose a mode: Bars → duration if you know the arrangement, or Duration → bars if you know the length you need.
- Enter the tempo in BPM. If you do not know it, measure it with the BPM tap calculator first.
- Pick the number of beats per bar. For almost all pop, Afrobeats, amapiano, R&B, hip-hop and dance music, that is 4.
- Enter the number of bars, or the target minutes and seconds.
- Read the result. The table underneath shows either common section lengths at your tempo, or practical bar counts that land near your target.
Tip: to time a whole song, add up the bars in each section of your arrangement — for example 8 (intro) + 16 (verse) + 8 (pre-hook) + 16 (hook) and so on — and enter the total. Our song structure planner is useful for mapping those sections out.
Example calculation
Bars to duration. A song at 100 BPM in 4/4 with 64 bars:
- Total beats = 64 × 4 = 256
- Duration = 256 × 60 ÷ 100 = 153.6 seconds = 2:33.6
- Each beat lasts 600 ms and each bar lasts 2.4 seconds.
Duration to bars. You want a three-minute track (180 seconds) at 100 BPM in 4/4:
- Beats = 180 × 100 ÷ 60 = 300
- Bars = 300 ÷ 4 = 75 bars
- 75 is not a tidy phrase length. The nearest 8-bar phrase is 72 bars (2:52.8), and the nearest 4-bar phrase is 76 bars (3:02.4).
- If you want exactly 72 bars to last exactly 3:00, the tempo would need to be 72 × 4 × 60 ÷ 180 = 96 BPM.
What does this result mean?
The headline figure is the exact musical length of the bars you entered, before any fade-out, reverb tail, count-in or silence at the start of the file. Use it to plan radio edits, fit a jingle or advert into a fixed slot, check whether a hook lands inside a short-form video clip, or estimate how long a new arrangement will run before you record it.
The beat and bar lengths are useful in their own right. Many producers set delay and reverb times in milliseconds from the beat length — at 100 BPM a quarter-note delay is 600 ms and an eighth-note delay is 300 ms.
How long is typical? Commercial releases vary enormously, and there is no correct length. A three-minute song at 100 BPM in 4/4 needs 75 bars; the same length at 120 BPM needs 90 bars. The faster the tempo, the more bars you need to fill the same time.
| Tempo (4/4) | 8 bars last | Bars in 3:00 |
|---|---|---|
| 90 BPM | 21.3 s | 67.5 |
| 100 BPM | 19.2 s | 75 |
| 112 BPM | 17.1 s | 84 |
| 124 BPM | 15.5 s | 93 |
| 140 BPM | 13.7 s | 105 |
Important limitations
- Constant tempo only: the maths assumes one steady tempo. Songs with tempo changes, rubato or live drift need each section calculated separately.
- Time signature changes: if a song switches between, say, 4/4 and 3/4, calculate each part on its own and add them together.
- What the BPM counts: in compound meters such as 6/8 or 12/8, the BPM might count eighth notes or dotted-quarter pulses. Choose the beats-per-bar setting that matches what your BPM actually measures.
- Real files are longer: reverb tails, fade-outs, pick-ups and silence are not included.
- Durations are shown to a tenth of a second; bar counts must be whole numbers.
Frequently asked questions
How do I calculate the length of a song from BPM?
Multiply the number of bars by the beats per bar, multiply by 60 and divide by the BPM. For example, 64 bars of 4/4 at 100 BPM is 64 × 4 × 60 ÷ 100 = 153.6 seconds, or 2 minutes 33.6 seconds.
How many bars are in a three-minute song?
It depends on the tempo. In 4/4, a three-minute song has 75 bars at 100 BPM, 90 bars at 120 BPM and 67.5 bars at 90 BPM. Use the Duration → bars mode to calculate it for your tempo.
How long is one bar at 120 BPM?
In 4/4, one bar at 120 BPM lasts exactly 2 seconds, because each beat lasts 0.5 seconds. An 8-bar phrase therefore lasts 16 seconds and a 16-bar verse lasts 32 seconds.
What should I choose for 6/8 time?
It depends on what your BPM counts. If your DAW or metronome clicks every eighth note, choose 6 beats per bar. If the BPM counts the two dotted-quarter pulses you feel in each bar, choose 2.
Why does the tool suggest a different tempo?
In Duration → bars mode, the “Tempo to hit target exactly” column shows the BPM at which a tidy bar count would last exactly your target length. It is optional — useful if you are writing to a fixed slot and have some freedom over the tempo.
Does this include fade-outs or reverb tails?
No. It calculates the musical time of the bars only. Allow extra time for fades, tails, count-ins and any silence at the start or end of the file.
