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About this tool
Work out how long a blend runs in bars, beats and seconds when the two tracks sit at different tempos.
The DJ Transition Length Calculator converts a blend measured in bars into real seconds at both tracks' tempos, and works out the pitch move needed to beatmatch them. One beat lasts 60 / BPM seconds, so a 16-bar blend in 4/4 is 64 beats — 31.0 seconds at 124 BPM but only 29.5 at 130. When you ride the tempo across rather than locking it, the elapsed time is the logarithmic mean of the two tempos, which the tool calculates exactly rather than averaging. For DJs planning set timings, radio edits and recorded mixes where the clock actually matters.
Open DJ Transition Length Calculator on AltFTool — it loads instantly in your browser.
Enter the values you already know.
Fine-tune the options to match your scenario.
Read the result and use it in your planning or reporting.
Shows the blend length at the outgoing tempo, the incoming tempo and while riding across.
Tells you whether the beatmatch fits a ±6, ±8, ±10, ±16 or ±50% fader, and suggests half or double time when it does not.
Flags whether the blend length lands on a whole 8-bar phrase, which is where most tracks change.
In 4/4 that is 128 beats, so at 128 BPM it runs exactly 60 seconds, at 124 BPM about 61.9 seconds and at 140 BPM about 54.9 seconds. The formula is bars x beats per bar x 60 / BPM.
The percentage is (incoming BPM - outgoing BPM) / outgoing BPM x 100. Going from 124 to 130 BPM needs +4.84%, which fits a standard ±8% fader; going from 124 to 140 needs +12.9%, which does not and requires a wide pitch range or a different approach.
Eight, sixteen or thirty-two bars, because dance music is built in eight-bar phrases and blending across a whole number of phrases keeps both arrangements aligned. Sixteen bars is the common default for house and techno; four or eight suits faster, busier genres.
Yes, unless key lock is on. Pitching a track up 6% raises it roughly one semitone, which will clash with a harmonically matched incoming track. Key lock preserves the pitch at the cost of some time-stretching artefacts, which become audible past roughly ±8%.
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