BPM to Milliseconds and Pitch Calculator

How to Convert BPM to Milliseconds

A minute holds 60,000 milliseconds, so one beat lasts 60,000 divided by the tempo. The calculator counts the beat as a quarter note unless a panel says otherwise.

Quarter note in milliseconds = 60,000 ÷ BPM

• A half note lasts twice as long as a quarter note. A whole note lasts four times as long.
• An eighth note lasts half as long as a quarter note. A sixteenth note lasts a quarter as long.
• A dotted note lasts one and a half times its plain value.
• A triplet note lasts two thirds of its plain value.

At 90 BPM a quarter note lasts 60,000 ÷ 90, which is about 666.7 milliseconds. A dotted eighth note lasts three quarters of that, which is 500 milliseconds.

Note Values at 120 BPM

The table shows the length of each note value at 120 BPM. The calculator shows the same table for any tempo you set.

Delay Times and LFO Rates

A delay set to a note value repeats in time with the song. Guitarists often choose a dotted eighth delay, so each echo falls between the beats and fills out the rhythm.

Each note value also appears as a rate in hertz. An LFO, or low-frequency oscillator, is a slow wave that moves a sound up and down. Set a tremolo, an auto-pan or an LFO to the rate in the table. The effect then moves in time with the tempo. The rate in hertz is 1,000 divided by the length in milliseconds. At 120 BPM a quarter note lasts 500 milliseconds, so its rate is two hertz. Tap any value in the calculator to copy it.

Reverb Pre-delay and Decay Time

Pre-delay is the short gap before a reverb begins. It keeps the start of each note clear. Decay time is how long the reverb takes to fade away. Engineers measure it as RT60, the time the sound takes to fall by 60 decibels. For each kind of reverb, the suggested decay is the note length minus the pre-delay.

Take 120 BPM with a pre-delay of a thirty-second note, which is 62.5 milliseconds. For a room reverb timed to a quarter note, the suggested decay is about 0.44 seconds. For a plate reverb timed to a half note, it is about 0.94 seconds. A plate is a bright studio reverb. The tail you hear also depends on the reverb and the mix, so treat these figures as starting points and adjust by ear.

Tap Tempo and the Length of a Section

To find the tempo of a song, tap along four or more times. The tempo is set from the average of your last eight taps. A metronome then clicks quarter notes at that tempo and accents beat one.

The bars-to-time panel gives the length of a section in seconds and in samples. At 120 BPM, eight bars of 4/4 last 16 seconds. Digital audio stores sound as samples, and 48 kHz means 48,000 samples each second. At that rate, 16 seconds is 768,000 samples. Audio editors use this number to set exact loop points.

The time-stretch panel fits a loop to a new tempo. Time-stretching changes the speed and keeps the pitch. Resampling changes the speed and the pitch together, as a faster tape does. The panel shows how far the pitch moves. A loop moved from 90 to 120 BPM by resampling rises by about five semitones.

Pitch to Frequency at A440

Most musicians today tune A4, the A above middle C, to 440 hertz. In equal temperament, the usual modern tuning system, all twelve semitones are the same size. The frequency of every note follows from A4.

Frequency = 440 × 2^(n ÷ 12), where n is the number of semitones from A4

C5 lies three semitones above A4, so its frequency is 440 × 2^(3 ÷ 12), which is about 523.25 hertz. Middle C, or C4, lies nine semitones below A4. Its frequency is about 261.63 hertz.

Turn the A4 reference dial to retune every note in the calculator. The concert pitch panel lists other references, such as 442 hertz and the lower pitch often used for Baroque music. The calculator also works in the other direction. Enter a frequency, such as a loud peak on a spectrum analyzer, and it gives the nearest note and its distance in cents. A cent is one hundredth of a semitone.

The tuning systems panel compares each interval in three tunings: equal temperament, pure ratios and Pythagorean tuning. Play the equal-tempered interval and then the pure one. In equal temperament you hear a slight pulsing, which musicians call beating.

Scales and Chords in Every Key

The scale explorer spells any scale correctly and builds a chord on each degree, with Roman numerals for each chord. The chord builder gives the spelling, the formula and the voicing of any chord in any inversion.

The transposer moves a whole progression. Paste chord symbols, including slash chords and bar lines, and shift them by semitones. The progression C, Am7, Fmaj7 and G7 moved up two semitones becomes D, Bm7, Gmaj7 and A7. The capo finder shows which open chord shapes to play for a song in a given key.

Decibels and Studio Figures

To turn a ratio into decibels, use 20 × log₁₀ for amplitude and 10 × log₁₀ for power. Doubling the amplitude of a signal adds about six decibels. Doubling its power adds about three decibels.

The studio panels show how much louder or softer a finished mix must be to match the loudness levels that streaming services commonly use. They give the size of an uncompressed audio file. They also find the axial modes of a rectangular room, the low notes that boom between two opposite walls. The lowest of these is 343 ÷ (2 × the distance between the walls in meters). Here 343 is the speed of sound in meters per second. In a room four meters long, this mode lies near 43 hertz.

How Musicians Use the Calculator

• Producers and mix engineers set delay, reverb and modulation in time with the song.
• Theory students check note lengths, frequencies and the spelling of scales and chords.
• Singers and guitarists move a song into a new key and find capo shapes for it.
• Audio editors cut sections and loops to the exact sample.