My understanding of the bottom number in a time signature is that this is how many beats there are in a whole note. So if the bottom number is 4, a whole note gets 4 beats. If the bottom number is 2 a whole note gets 2 beats and if the tempo is 60bpm then it lasts 2 seconds instead of 4.

Is this right?

  • 2
    See my answer to a question about 6/8. "The bottom number is the beat" is an oversimplification that helps when starting to explain meter to beginners, but doesn't hold up for compound time. Commented Sep 12, 2022 at 13:24
  • I've tried to ask almost this as well in this question. See if those answers answer your question!
    – EdvinW
    Commented Sep 12, 2022 at 20:41

3 Answers 3


"the bottom number in a time signature is ... how many beats there are in a whole note"

I wouldn't think of it as beats, necessarily; but certainly the denominator represents the note duration that fits 'that many' in a whole note.

In the US, of course, the maths is done for you: a quaver is an eighth note, so anything over 8 is in eighth notes; a minim is a half note, so anything over 2 is in half notes.

The problem with thinking in terms of 'beats in a whole note', is that this doesn't help you much with 3/4, or 5/4, or 9/8; unless your maths is very good.

(And 3/8 is often beated in one; 6/8 is usually beated in 2; 4/4 might be beated in 8 or 2, etc, etc.)

Also: metronome speeds are usually marked in terms of a note duration e.g. 'minim = 60', rather than just '60bpm'. So the 'calculation' you're making of the denominator in terms of a whole note doesn't really apply.

  • What does the half note in 60 mean. 60 half notes in 60 seconds?
    – 7321
    Commented Sep 13, 2022 at 14:16
  • @7321 That means "There are 60 half notes in a minute." There are 60 beats per minute, and those beats are half notes. Not quarters, nor eighths, nor anything else. Yes, 1 per second.
    – benwiggy
    Commented Sep 13, 2022 at 15:06

A time signature is similar to a fraction. In that the bottom number tells what the divisions are, while the top tells how many of them there are.

So, in 4/4 the bottom 4 tells each 'beat' is a crotchet (quarter note), while the top 4 tells there are 4 of them in each bar. Similarly with 3/4. 3 crotchets per bar. 5/4 tells 5 crotchets per bar, unsurprisingly.

6/8 tells there are 6 quavers in each bar, which is the same as 3/4 mathematically, but actually doesn't reveal that the rhythm of the bar is quite different, though. That's often where the confusion between 3/4 and 6/8 is found. 7/8 unsurprisingly tells 7 quavers (eighth notes) in each bar - but again, a little like 6/8, doesn't give a clue in itself how those quavers are grouped, rhythm wise.

The concept of a 'whole note' :- a whole note is called a semibreve, which is made up of two minims,(1/2 notes) or 4 crotchets,(1/4 notes). It is the hollow egg-shaped note, with no stem. It doesn't have too much bearing on things - except that it is the 'whole' that is divided, as explained in this paragraph. A whole note will fit into one bar of 4/4, but not into a whole bar of 3/4. Hence 3/4 gets called 'three-quarter time' quite often. That, and after all, it looks exactly like the fraction - 3/4!

  • 1
    Thanks for addressing the OP's core confusion about "whole note"! Commented Sep 12, 2022 at 13:25

Yes, that's correct. Just keep in mind that a whole note need not fit in a single measure. For example, in 6/8 time, a whole note gets eight beats, but each measure only has 6. Similarly, for 3/4 time, a whole note gets four beats, but each measure contains only three.

See also I don't understand the bottom number in a time signature, which explains the same concept in a different way.

There is also a concept of "irrational" time signatures, such as 4/3 or 6/10. The rule holds here as well. In 4/3, a whole tone would receive 3 beats, and a measure would contain four 1/3-beats. ("Irrational" in this sense is distinct from the mathematical idea of irrational numbers.)

  • Wha??? Was the question edited after you answered? If the time signature is 6/8 then there are not 8 beats in a whole note. There aren’t even two beats. A whole note always equals four quarter notes. A whole rest may be used as a measure long rest even when the measure is not four quarters long. A measure of 6/8 contains two beats, not six. Commented Sep 12, 2022 at 22:16
  • @ToddWilcox In 6/8 time, it is frequently taught that the eighth note get the beat. There are eight eighth notes in a whole note; therefore, eighth beats.
    – Aaron
    Commented Sep 12, 2022 at 22:54
  • Seems like it’s frequently taught wrong Commented Sep 13, 2022 at 0:22
  • @ToddWilcox That's been the standard for every teacher I've had, including conservatory. I'd never heard it taught as 2 beats per measure until I got here. It was always "six beats the the measure; the eighth note gets one beat." It's not wrong; just different than what you're used to.
    – Aaron
    Commented Sep 13, 2022 at 1:15
  • I was literally talking with a professor a few hours ago about 12/8 and 9/8 time and he definitely would have said I was wrong if I counted those measure with 12 or 9 beats respectively. We had a whole discussion about how I should be thinking of those time signatures. I can’t imagine how you could have conservatory teachers suggesting you count 6/8 as "1 2 3 4 5 6" instead of "1 & uh 2 & uh" (or equivalent). How could you follow a conductor counting 6/8 in six? You couldn’t even play drums for Chevelle if you played 6 beats in 6/8. Commented Sep 13, 2022 at 2:54

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