Audio Calculators

Convert notes to hertz, tempo to milliseconds and gain to decibels.

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Note and frequency

NoteOctaveA4 reference (Hz)

Frequency440.00Hz

Frequency (Hz)

Nearest noteA4

Cents off0.0

Equal temperament, tuned to the A4 reference above. Most music uses 440 Hz; period ensembles often use 415 Hz.

Tempo to milliseconds

Tempo (BPM)

Note	Straight	Dotted	Triplet
1/1	2000.0 ms	3000.0 ms	1333.3 ms
1/2	1000.0 ms	1500.0 ms	666.7 ms
1/4	500.0 ms	750.0 ms	333.3 ms
1/8	250.0 ms	375.0 ms	166.7 ms
1/16	125.0 ms	187.5 ms	83.3 ms

Set a delay, a tremolo or an LFO to one of these times and it lands in step with the tempo. A dotted note lasts half again as long; a triplet lasts two thirds.

Gain and decibels

Gain factorLevel (dB)

Reference points

Gain factor	Decibels
x2	+6.02 dB
x0.5	-6.02 dB
x10	+20.00 dB

These are amplitude decibels, the ones a fader shows: doubling the amplitude is about +6 dB, and ten times the amplitude is +20 dB.

Three conversions come up again and again in music and audio work, and none of them is worth doing on paper. This page turns a note name into a frequency and back, a tempo into every useful delay time in milliseconds, and a gain factor into decibels. Everything recalculates as you type, nothing is saved, and nothing is uploaded.

How to use it

For note to frequency, pick the note name and the octave and read the result underneath. The A4 reference field sets the whole scale, so drop it to 415 Hz and every note moves with it.
For frequency to note, type a value in hertz. The page names the nearest note and shows how many cents above or below it you are, which is the quickest way to find out whether a recording sits in tune.
For tempo to delay time, type the BPM. The table gives whole, half, quarter, eighth and sixteenth notes in three columns: straight, dotted and triplet. A dotted note lasts half again as long as the straight one; a triplet lasts two thirds.
For gain and decibels, type into either box and the other one follows. The reference table underneath keeps the three values worth memorizing in view while you work.
Note that these are amplitude decibels, the ones a fader and a level meter show. Doubling the amplitude is about +6 dB, and ten times the amplitude is +20 dB.

What you can use it for

Putting a delay in time with a track. Take the delay time for an eighth or a dotted eighth at your tempo and type it into the plugin. Dotted eighths are the classic setting for a rhythmic slap that pushes against the beat.

Setting an EQ or a notch filter to a note. If a bass note is booming in a room, look up its frequency and cut there, rather than sweeping blindly and hoping.

Working out what a fader move is actually worth. Six decibels sounds like a small number until you notice it is double the amplitude, and a gain factor puts that in plain terms.

Checking whether a recording is in tune. Read a sustained note with a spectrum analyzer or a tuner, type the frequency here, and the cents figure tells you how far the recording sits from concert pitch.

Converting between pitch standards. Type the same note at 440 Hz and again at 415 Hz to see exactly how far apart modern and baroque pitch sit, or use 442 Hz to match an orchestra.

Common values worth knowing by heart

A4 is 440 Hz by international agreement, and middle C, written C4, is 261.63 Hz at that reference. An octave up doubles the frequency and an octave down halves it, so A5 is 880 Hz and A3 is 220 Hz.

At 120 BPM a quarter note is exactly 500 ms. The general form is 60000 divided by the tempo, so 100 BPM gives 600 ms and 140 BPM gives about 428.6 ms. Halve for eighths, halve again for sixteenths.

Plus 6 dB is roughly double the amplitude and minus 6 dB is roughly half. Plus 20 dB is ten times. Perceived loudness is a different thing again: it takes about 10 dB before most listeners call something twice as loud.

One semitone is a frequency ratio of the twelfth root of two, about 5.95 percent, and it is divided into 100 cents. That is why a note two semitones up is not twice anything, and why cents rather than hertz are the useful unit for small tuning differences.

Accuracy and limits

Every note here uses equal temperament, where the octave is split into twelve identical steps. Just intonation, meantone and historic temperaments place several notes a few cents away from these values on purpose, so the cents readout tells you the distance from equal temperament rather than the distance from correct.

The delay times are exact note lengths at a constant tempo. Music that was played rather than programmed drifts around the grid, music with a tempo map moves under you, and some plugins round their own time display to the nearest millisecond. Use the number as a starting point and trust your ears for the last few milliseconds.

These are amplitude decibels, calculated as twenty times the base ten logarithm of the ratio. Power decibels use ten times instead, so the same ratio reads half as many decibels, and loudness measurements such as LUFS are a different scale again with frequency weighting built in.

Frequently asked questions

How do I convert BPM to milliseconds?

Divide 60000 by the tempo to get one quarter note in milliseconds. At 120 BPM that is 500 ms, at 90 BPM about 666.7 ms. Halve it for an eighth, halve again for a sixteenth, multiply by 1.5 for a dotted note and by two thirds for a triplet.

What is the frequency of A4 and middle C?

A4 is 440 Hz under the modern standard, and middle C, C4, is 261.63 Hz. Both move together if you change the reference: at 432 Hz, middle C lands at about 256.87 Hz.

What is the delay time for a dotted eighth at 120 BPM?

375 ms. A quarter note is 500 ms at 120 BPM, so a straight eighth is 250 ms and a dotted eighth is one and a half times that. Type 120 into the tempo box and the whole table appears.

How many dB is twice as loud?

Two different questions hide in that one. Doubling the amplitude, which is what a fader does, is about +6 dB. Sounding twice as loud to a listener takes closer to +10 dB, because hearing compresses the scale. The calculator answers the first question; only your ears answer the second.

What is a cent?

One hundredth of a semitone, so 1200 cents make an octave. Differences under about 5 cents are inaudible in most contexts, differences of 10 to 20 cents beat audibly against another instrument, and 50 cents is a quarter tone.

Why does my measured frequency read a few cents off?

Usually because the source is not exactly at concert pitch, or because the instrument itself is not perfectly equal tempered. Tape and vinyl transfers drift, older recordings were made at other pitch standards, and strings and voices bend notes on purpose. Change the A4 reference until the cents figure sits near zero and you have found the pitch the recording was actually made at.