Calculate interval, frame count, shooting duration, and final video length for time-lapse projects.
A time-lapse squeezes hours into seconds, and the whole calculation rests on two relationships: frames equals shooting duration divided by interval, and final video length equals frames divided by the playback frame rate. Enter any two of the four quantities and the tool derives the other two, converting between seconds, minutes, and hours as it goes. What catches most people is how short the finished clip is: two hours of shooting at one frame every 10 seconds yields only 24 seconds of video at 30 fps, and the playback rate you choose changes that number as much as the interval does.
A concrete input and expected output from the current implementation.
Input
Shooting duration: 2 h 00 m | Interval: 10 s | Playback rate: 30 fps
Expected output
720 frames, final video length 24 s
Two hours is 7200 seconds, and at one frame every 10 seconds that is 720 frames. Played back at 30 fps, 720 frames lasts 24 seconds, so the frame count and the clip length both fall out of the two values you entered.
The math is fixed: shooting duration equals frames times interval, and final video length equals frames divided by the playback rate. Because four quantities sit in two equations, any two known values determine the other two. Give it shoot time and interval and it returns frame count and clip length; give it clip length and frame rate and it works backwards to the interval and shooting duration.
Every field accepts seconds, minutes, or hours, and values are converted to a common unit before the equations run, so 2 hours, 120 minutes, and 7200 seconds describe the same shoot. The playback rate is a real input, not a footnote: 24, 25, and 30 fps each give a different clip length for the same frame count, so the rate you will actually render at belongs in the calculation.
Many cameras cap an interval-recording session at a few hundred frames, and 999 is a common limit, so check the manual. Re-arm the timer for a second session when it stops, or use an external intervalometer that has no such cap. The calculator still works: plan the shoot as multiple sessions, add the frame counts, and allow a small gap where you restart.
The usual cause is a frame-rate mismatch: you planned for 24 fps but rendered at 30, which shortens the clip by 20 percent. Dropped frames are the other cause, typically when the shutter speed exceeded the interval and some exposures never happened. Recheck both the fps you entered and the interval actually set on the camera before suspecting the math.
The example and behavioral notes were checked against the browser implementation. Standards and primary references below define the relevant format, formula, or platform behavior.
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