Song Length Calculator (BPM & Bars)

This song length calculator turns bars, BPM and time signature into running time. Build the arrangement section by section, each with its own bar count, tempo and meter, and it adds them up. It can also run the math backwards: how many bars fill a target length, or what BPM fits a set number of bars into a set time. A fourth mode shows how a tempo change or playback speed changes the length. Every mode includes a BPM-to-milliseconds table for delay and reverb times, with straight, dotted and triplet note values.

It is meant for songwriters mapping out a form, producers planning a session to click, composers cutting a cue to picture, and anyone checking how long a podcast or audiobook will take at a faster playback speed. The math is simple, but it is easy to get wrong in compound meters. Is your 6/8 tempo counted in dotted quarters or in the quarter notes your DAW shows? The “BPM counts” switch handles that explicitly.

Song length formula: BPM, bars and time signature

Seconds = bars × beats per bar × 60 ÷ BPM. Tempo is beats per minute, so one beat lasts 60 ÷ BPM seconds. At 120 BPM that is 0.5 s. Multiply by the beats in a bar to get bar length, and by the number of bars to get the section length. Add the sections together for the whole song.

The time signature supplies the beats per bar. As Hutchinson's open textbook puts it, the top number tells you “how many” and the bottom number tells you “of what”: 3/4 is three quarter notes per bar and 7/8 is seven eighth notes. Open Music Theory adds the rule that matters for timing: when the top number is 6, 9 or 12, the meter is compound. The beat is then a dotted note split into three, and the bar has 2, 3 or 4 beats. So 6/8 has two dotted-quarter beats, not six. The Berklee Online songwriting handbook describes the same convention for charts: the pulse is written as quarter notes, “or dotted quarter notes for 6/8 meter.”

Beat or quarter note: which BPM do you have?

This is where most mistakes happen. A 6/8 ballad charted at dotted quarter = 60 feels like 60 BPM, but a DAW that counts quarter notes shows the same tempo as 90 BPM, because a dotted quarter is 1.5 quarter notes. Both give a 6/8 bar of exactly 2 seconds. Enter them with the wrong setting, though, and the song comes out 50% too long or a third too short. Cut time (2/2) works the same way: a half-note beat of 80 is a quarter-note tempo of 160.

For irregular meters such as 5/8 and 7/8, the calculator counts the bottom-number note (an eighth) as the beat, because the uneven groupings such as 2+2+3 have no single beat length. If your click counts the groups rather than the eighths, switch to quarter-note BPM and enter your DAW tempo.

Song lengths at common tempos

Here is a quick way to check a whole song in 4/4 at one steady tempo. The columns step in 16-bar blocks.

How many bars for a target length?

Rearranged, the formula gives bars = seconds × BPM ÷ (60 × beats per bar). The answer is rarely a whole number. You can round up and trim in the edit, round to the nearest 4 or 8 bars to keep phrases even, or nudge the tempo, which the BPM mode solves exactly. The table shows exact bar counts in 4/4.

Worked example: an arrangement with a tempo and meter change

The default arrangement is a common pop form: intro 8, verse 16, chorus 16, verse 16, chorus 16, bridge 8, chorus 16, outro 8. That is 104 bars at 120 BPM in 4/4. Each bar is 2 seconds, so the song runs 3:28. Now take a song at 96 BPM: intro 8, verse 16 and chorus 16 in 4/4, then a bridge of 8 bars in 6/8 at dotted quarter = 72, then a last chorus of 16 bars pushed to 104 BPM. The 4/4 sections at 96 are 2.5 s per bar, so 40 bars = 100 s. The 6/8 bridge is 2 beats × 60 ÷ 72 = 1.667 s per bar, so 13.3 s. The final chorus is 16 × 4 × 60 ÷ 104 = 36.9 s. Total: 2:30. Enter the same sections in the calculator, and the chart shows how much of the running time each section takes up.

BPM to ms: delay time table

A quarter note lasts 60,000 ÷ BPM milliseconds. Every other value is a multiple of that. Hutchinson's textbook defines the two modifiers: a dot “increases the duration of that note by half,” so dotted = × 1.5. A triplet puts three notes “within the span” of two, so triplet = × 2/3. The table uses quarter-note BPM, so for 6/8 counted in dotted quarters, first multiply your BPM by 1.5. The calculator does this for you.

To convert milliseconds to hertz, as for an LFO or tremolo rate, use Hz = 1,000 ÷ ms. A quarter note at 120 BPM (500 ms) is 2 Hz, and a 16th note (125 ms) is 8 Hz.

Note values in beats

In 4/4 a whole note fills the bar, a half note fills half of it, and each shorter value halves again. These are the note lengths behind any rhythm calculation, measured in quarter-note beats.

Tempo changes and playback speed

Speeding up a track shortens it in exact proportion: new length = old length × old BPM ÷ new BPM. The speed factor is new BPM ÷ old BPM, so 120 → 126 BPM is 1.05×, and a 4:00 song drops to 3:49. The same ratio applies to spoken audio: the speed setting on a podcast or audiobook app is that factor. An 8-hour audiobook at 1.5× takes 5:20:00. Gradual tempo changes, such as a ritardando into the last chorus, can't be captured by one BPM per section. Split the passage into shorter sections at the average tempo of each, or measure the render.

Common mistakes

• Mixing up beat BPM and quarter-note BPM in 6/8, 12/8 or cut time. Check which one your chart or DAW shows.
• Counting the count-in. A one-bar click-in before the downbeat usually isn't part of the release. Leave it out, or add it as its own section if it stays in the file.
• Forgetting pickups and tails. A two-beat pickup, a final held chord or a reverb ring-out isn't a full bar. Add the extra seconds by hand.
• Assuming a half-time feel halves the BPM. A half-time drum groove at 140 BPM still runs 140 BPM on the grid. Only the feel changes, not the length of a bar.

Working with time on its own rather than music? The hours from now calculator tells you what time it will be when a recording session or a long render finishes. For a song timed to a date, such as a first dance, the anniversary calculator counts the days.

Frequently asked questions

Sources & method

• Open Music Theory (Gotham et al.) — Meter: simple vs compound, time signatures
• Hutchinson, Music Theory for the 21st-Century Classroom (University of Puget Sound), §4.1 Time Signature
• Hutchinson, Music Theory for the 21st-Century Classroom, §4.2 Durational Symbols
• Hutchinson, Music Theory for the 21st-Century Classroom, §4.3 Dots and Ties
• Hutchinson, Music Theory for the 21st-Century Classroom, §4.5 Tuplets
• Berklee Online Songwriting Handbook — choosing a tempo (BPM; dotted-quarter pulse in 6/8), PDF

Results are estimates for general information. Found an error? It helps everyone — see our methodology.