Seamless loop crossfade calculator

It validates that the overlap is physically sensible by rejecting any crossfade longer than half of the source. No audio is uploaded, decoded, analyzed, or changed; the result is deterministic timing information you can apply in an editor, sampler, game engine, installation, or automated media workflow.

Place the overlap at the end of the source

A loop crossfade uses the final portion of a track and the opening portion of its next repetition at the same time. Enter the complete track duration in seconds and the overlap you want. The calculator subtracts the crossfade length from the track duration to locate the crossfade start. For a 120-second track with a 5-second overlap, the outgoing region begins at 115 seconds. From that point until the source endpoint, the end fades down while a copy of the beginning fades up. The response gives this position as crossfade_start_seconds, making it suitable for a marker, edit decision list, sampler configuration, or render instruction. The calculation assumes that both supplied values use seconds and refer to the same source timeline. It does not choose a musically appropriate point, inspect waveform phase, detect beats, or determine whether the beginning and ending material sound compatible. Those creative and signal-level decisions remain separate; this result supplies the exact window after you have chosen an overlap length.

Understand the perceived loop duration

Crossfading overlaps time that would otherwise play sequentially, so the listener does not experience the full source duration between matching positions on successive passes. The perceived loop duration is the track duration minus the crossfade length. It therefore equals the crossfade start position when the track begins at zero. A 120-second source with a 5-second crossfade repeats on a 115-second cycle: during the last five seconds of one pass, the first five seconds of the next pass are already sounding. This value is useful when synchronizing animation, lighting, gameplay events, transport markers, or other repeating systems to the audible cycle rather than to the unedited file length. A zero-length crossfade is valid and leaves both the start point and perceived duration equal to the original track duration. The calculator reports decimal seconds without converting them to samples or timecode. If your production system requires sample-accurate boundaries, convert the returned seconds using the project sample rate and apply the rounding policy required by that system.

Keep the requested crossfade within a usable range

The overlap may be zero, but it cannot be negative and cannot exceed half of the track duration. The half-duration rule ensures that the opening and closing regions used by the crossfade do not extend through one another and compete for the same central material. A 30-second track therefore accepts a crossfade of up to 15 seconds and rejects anything longer. The exact halfway value is allowed: it produces a crossfade start and perceived cycle of 15 seconds. Both inputs must be finite numbers, and the track duration must be greater than zero. Use measured source duration rather than a rounded display label when accurate synchronization matters. This capability performs timeline arithmetic only; it does not render equal-power or linear fade curves, compensate for latency, trim silence, align transients, or verify that the resulting seam is inaudible. After placing the window, audition the transition and inspect level, phase, rhythm, ambience, and any encoded output. The browser calculation is available directly, while each automated API request costs $0.002.