Chord progressions
Twenty progressions in twelve keys, with symbols and degrees, an arpeggiated listen and a direct hand-off to the music paper.
en / tools / bpm-and-length
BPM and length
How long a section lasts, what tempo makes it last that long, how many bars fit — in any metre, odd ones included.
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Length
1:04,000
One bar lasts 0:02,000 · 4 quarter notes to the bar
Quarter notes per minute: the number you type into your DAW’s tempo field.
Minutes and seconds, or just seconds: 1:04, 64, 64.5, 1:04.500. The dot and the comma mean the same thing.
Here BPM is the DAW’s: quarter notes per minute, in any metre. This site’s metronome counts the beats of the METRE instead, and in 6/8 there are two to the bar — so at 120 a bar of 6/8 lasts one second here and a second and a half there. Both are standard conventions: they agree in 2/4, 3/4 and 4/4, and they part company exactly where it pays to know.
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How it works
- Pick the question: how long, at what tempo, or how many bars.
- Type the metre and the two numbers you know. It works out the third.
- Copy the result: the length comes out as 1:04.000, which is the form you paste.
Why it exists
Because it is a sum you do constantly and get wrong in your head.
A brief says thirty seconds. The track is at 128 BPM. How many bars fit into thirty seconds? Another says the intro should last as long as the first eight bars of the verse, and you want to know where to cut. Another again: you have a 1:45 video and you need the tempo that fits a whole number of bars into it.
Three different questions, and one equation solved for three different unknowns. That is why they are one tool and not three panels side by side: three panels would ask for the metre three times and the tempo three times, and let the three copies drift apart in front of you.
About the metre
The metre is written as two numbers, top and bottom, rather than picked from a list of four. That is not completeness for its own sake: the metres that actually need this sum are precisely the ones a short list leaves out. 7/8 and 5/4 are where nobody does the arithmetic in their head, and 12/8 is where they do and get it wrong.
What matters is how many quarter notes fit in a bar, and it comes from the two numbers: four in 4/4, three in 6/8 — six eighths are three quarters — six in 12/8, and three and a half in 7/8. The fractional number is correct and must not be rounded: half a quarter note per bar, over thirty-two bars, is sixteen beats.
About BPM, and a difference worth knowing
Here BPM is the DAW’s: quarter notes per minute, in any metre. It is the number you type into Logic’s or Ableton’s tempo field.
This site’s metronome, on the other hand, counts the beats of the metre, which in 6/8 are two to the bar. Both are standard conventions, and in simple metres — 2/4, 3/4, 4/4 — they give the same number, which is to say almost always. They part company in 6/8: at 120, a bar lasts one second here and a second and a half there. Neither one is wrong; that is why it is written down in both, instead of being discovered by getting a delivery wrong.
About typing a length
The field takes 1:04, 64, 64.5, 1:04.500. The dot and the comma mean the same thing, because
the field is filled in by an Italian who writes a comma and an English speaker who writes a dot, and
in a field of seconds neither of them can mean “thousands separator”.
One thing that looks like a quibble and is not: 1.5 is one thousand five hundred milliseconds,
not one thousand and five. Decimals are padded to the right, like on a stopwatch. Reading them as
whole numbers would be wrong by a factor of a hundred on a spelling anyone would use.
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