Half-Time and Double-Time Calculator

How are half-time and double-time tempos calculated?

Multiply the tempo by a fixed ratio: ½ for half-time, 2 for double-time. The notes on the grid do not move; only the pulse a listener counts as the beat changes. Five ratios cover the common re-hearings of a groove.

related tempo = BPM × ratio (½, 2, ⅔, 3/2 or ¼)

• Half-time (×1/2) moves the backbeat from beats 2 and 4 to beat 3, so the groove feels half as fast.
• Double-time (×2) treats eighth notes as the beat, so the groove feels twice as fast.
• Dotted-quarter pulse (×2/3) counts a beat every three eighth notes, the feel of compound meters such as 6/8.
• Quarter-note-triplet pulse (×3/2) places three even beats in the space of two.
• Quarter-time (×1/4) counts one beat per 4/4 bar.

How to use the calculator

1. Enter the tempo

   Type the BPM, use the slider and steppers, or press Tap tempo in time with the music.

2. Read the table

   Each row gives the Feel, the Factor, the resulting BPM and What changes in the rhythm. Half-time and double-time are highlighted.

3. Send a value on

   Use the Send links to open the tempo in the metronome, delay or song-length tools.

Worked examples: related tempos for four grooves

Every tempo has a family of related pulses. The values below use the tool's five ratios.

Where half-time and double-time feels appear

Many styles are defined by which pulse the listener follows. Dubstep is typically produced at 140 BPM with the snare on beat 3, so it is heard at 70 BPM; the dubstep tempo guide explains the convention. Drum and bass at 174 BPM is often felt as 87 BPM for the same reason.

DJs use the related tempos to mix across genres: a 140 BPM track and a 70 BPM hip-hop instrumental share the same grid, while 128 BPM and 174 BPM do not, as the pitch-fader percentage tool shows. Drummers use the dotted-quarter column to switch a straight groove into a 6/8 or 12/8 feel over the same eighth notes.

For practice, set the practice metronome to the half-time value and count the click as beat 1 and beat 3; slow passages then keep the original grid.

What the calculator cannot decide

It lists the related tempos but cannot tell which one the music is in. The correct BPM depends on where the drummer places the backbeat and how the chart is written. Tempo-detection software faces the same ambiguity, which is why the tap-along BPM finder shows half and double values next to its estimate. Values outside the usual 20–300 BPM range, such as a quarter-time of 22.5 BPM, are shown for counting only.

Questions