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Tempo (BPM) to Millisecond Delay Interval Calculator

Updated on April 19, 2013
This is not the calculator. Just a cool digital audio effects image.
This is not the calculator. Just a cool digital audio effects image.

Have you ever needed to calculate an eighth note, or a sixteenth note delay in milliseconds, but weren't exactly sure how to do it?

Chances are, if you're reading this article, the answer is yes. Subsequently, you thought to yourself,

"You know, there should be a quick and easy calculator that tells me, no matter what tempo I'm playing in, the exact millisecond delay interval for a quarter note, eighth note, sixteenth note, or whatever ... what the hell?!"

I've thought the same thing so many times, that I finally just broke down and created one. Here it is ...

The Tempo, in Beats Per Minute (BPM) to Millisecond Delay Interval Calculator

I can't post Javascript in here (Hubpages) so I have to link you to my other site to use the tool. I hope you enjoy it! Below we'll talk a little bit about the tool.

How does the calculator work?

While the process of figuring out the exact millisecond delay interval between the various note lengths, like eighth note, sixteenth note, etc, is not a difficult mathematical calculation, it is certainly cumbersome enough to be a pain in the ass when you're recording, and just need an accurate delay, or chorus, or reverb effect.

That's why we have computers, right? To do extremely tedious tasks, that we can probably do ourselves, but with extreme speed, precision, and greatly reduced chances for silly human error?

Let's actually look at the tool, if you haven't clicked the link yet:

Here is a screen shot of the tempo to millisecond calculator

It's a little squished, and compressed [damn Hubpages] but you can just click the link above to see the real thing, so deal with it.
It's a little squished, and compressed [damn Hubpages] but you can just click the link above to see the real thing, so deal with it.

Let's continue our discussion about how it works ...

I know some of you want to see the math, to either check it out, or just to learn it. So here it is:


where, inputeBPM = variable that takes the user BPM input in the web form, qtrN = Quarter Note variable and sixteenN = Sixteenth Note Variable, and so on ....

The above snippet is pulled from some javascript code. Obviously this is not the whole calculator, but describing the event handlers, functions, writing the output to the page, and actually calculating all the different intervals is beyond the scope of this article.

The basic flow of how it works is like this ...

  1. User inputs the tempo, in beats per minute, that they're working with. Say, 148 for instance. 
  2. User then presses the "calculate" button.
  3. The code grabs the user input from field (bpm.value) and assigns it to the inputBPM variable.
  4. I start with the quarter note, because it corresponds exactly to the concept of a "beat".
    • For instance, at 120 beats per minute (BPM), there are exactly 120 quarter notes, in a 4/4 time signature, in exactly 60 seconds. This means there are 2 quarter notes for every second of time that passes (120/60). So, if there are 1,000 milliseconds in a second, then at 120 BPM, each quarter note interval is precisely 500 milliseconds long. So, I like to start with the Quarter note.
  5. The section at the end of the quarter note statement: (result * 100000)/100000 is required, by necessity of using Javascripts "round" function (Math.round[expression]) to get the millisecond value with a precision level of 5 decimal places.
  6. Each note is then calculated from the quarter note. At this stage, each value is allowed to repeat infinitely, to preserve accuracy.
  7. Each note is then rounded to the fifth decimal place.
  8. The values are then written to the page in their appropriate places. For instance: whole, half, quarter, eighth, sixteenth, thirty-second, sixty-fourth, and so on ...
  9. The calculator even calculates some of the "odd" or "non-conventional" intervals like the sixth, twelfth, or twenty-fourth note.
    • I'm aware those are not technically (According to traditional music notation) legitimate intervals. They are either dotted, temporary time signature changes, or whatever ... I know.
  10. You can then change your Tempo / BPM and press calculate again, and instantly get all new results.

Here are some hardware effects processors

Pardon me, but why would I ever need to calculate the delay intervals in milliseconds?

There is a chance that, even the musically inclined, might not see the importance of having these values precisely targeted to your tempo (in beats per minute).

Having these values are especially important when using digital signal processing, digital effects plug-ins for computer software, or when using hardware devices like foot-pedals (stomp boxes), and rack-mounted effects processors.

Essentially all audio effects are manipulating and/or duplicating the audio signal. In nearly all cases, the audio signal (the wave) is duplicated. The copies are then processed, or shifted, and integrated back into the original signal. These adjustments are almost always calculated in milliseconds.

As an artist, attempting to create the most sonically appealing result, having precise control of the millisecond values in these various effects is invaluable. If you're just moving the slider by ear, until it sounds "good", then you'll get a similarly acceptable result. But why not use a precise millisecond delay value in your reverb or tap-delay effect? Why not make it near perfect? That's what the pros do! And now you can too with my simple to use tempo to millisecond delay interval calculator.

Here is the link again, in case you missed it ...

The Tempo, in BPM (beats per minute), to Millisecond Delay Interval Calculator

I hope you all get some good use out of this, and enjoy it! Please leave a comment if you think this tool could be easily improved upon, or if there is another simple calculator thing out there that you're surprised doesn't exist yet.

Be peaceful on your way,



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    • profile image

      ChronoCross 5 years ago

      wow this great! This helping my game music project, thanks a lot!

    • Time Spiral profile image

      Time Spiral 6 years ago from Florida

      Thanks, guys! I'd love to hear what you come up with.

    • profile image

      Laro 6 years ago

      G R E A T ! ! ! Thank you very very much!!!

    • Painter Penfield profile image

      Painter Penfield 6 years ago from Tampa Bay area Florida

      Time Spiral you are scary smart! Believe it or not, I could really use this in the recording studio at home. Thanks for a well thought out and fascinatingly useful tool invention. You are right...why settle for slider fiddling when you can get the computerized coolness of the real math? ;) I want to play around with this in the studio now. Thanks for the inspiration.