Timecode Frame-Rate Converter

Two questions that sound like one

"What does this timecode become at the other frame rate?" has two different correct answers, and picking the wrong one is the most common frame-rate conversion mistake in post. The question is really two questions:

• Same moment (co-timed): where does this exact real-world instant land at the target rate? Use this for dual-delivery timelines (a 24 fps master and a 25 fps web cutdown that must reference the same real second), subtitle and marker conversion, or syncing a cue sheet across two versions of a project.
• Conform (same frame number): frame N simply gets relabeled at the target rate — the footage itself is retimed, so it now runs for a different real duration. Use this for a PAL speed-up conform, a 24→25 delivery that intentionally changes runtime, or explaining why an NLE reports a different clip length after a project frame-rate change.

Mixing the two up produces timecodes that are numerically plausible but describe the wrong thing — a marker that's 4% off, or a duration that silently assumes footage was retimed when it wasn't.

Worked example: the clean case (Same moment)

01:00:00:00 at 24 fps is exactly 86,400 frames and exactly 1 real hour (86,400 ÷ 24 = 3,600.000 s). Ask "same moment at 25 fps" and the target frame is 3,600 × 25 = 90,000 exactly — which converts back to 01:00:00:00. Same label, purely because both rates land on a clean hour boundary; it is easy to mistake this for evidence that 24 and 25 timecode always line up. They don't.

Worked example: the case that doesn't align

Take 00:00:10:12 at 24 fps: that is 252 frames, or exactly 10.5 real seconds (252 ÷ 24 = 10.5). Asking for the same moment at 25 fps gives a target frame position of 10.5 × 25 = 262.5 — there is no frame 262.5, so the instant lands mid-frame. The converter floors to frame 262 (label 00:00:10:12 again, coincidentally the same digits at 25 fps) and reports the remainder: 0.5 of a 25 fps frame period (40 ms) is a 20 ms residual — the queried instant actually lands 20 ms into that frame, not at its start. Ignoring that residual is how a "frame-accurate" marker drifts by half a frame after a rate change.

Worked example: the PAL conform (this is the one that changes runtime)

Relabel that same 01:00:00:00 / 86,400-frame hour of 24 fps footage as 25 fps without changing the moment — i.e., conform it, frame for frame. Frame 86,400 relabeled at 25 fps is 86,400 ÷ 25 = 3,456 seconds = 57 minutes 36 seconds, giving the timecode 00:57:36:00. The hour of film now plays back in 57:36 — about 4.2% faster (25 ÷ 24 ≈ 1.0417×) — which is exactly why PAL-conformed features historically ran a few minutes shorter than their NTSC/film counterparts, and why the audio needs a pitch correction (or is left to run sharp, the classic "PAL speed-up").

The drop-frame gotcha

Converting to or from 29.97 drop-frame must go through frame counts, never through copying digits. Drop-frame labels skip numbers 00 and 01 at the start of every minute except each tenth minute, so a DF label is not a linear count of anything — you decode it to an absolute frame count first (undoing the skip), do the real-time or frame-number math, then re-encode the result into DF labels (reinserting the skip) if the target is 29.97 DF. As a same-moment example: 01:00:00:00 at 23.976 is 86,400 frames = exactly 1:00:03.600 real time (23.976 runs 0.1% slow). Converting that same moment to 29.97 DF gives target frame 108,000 (nominal count) — which the drop-frame algorithm reads out as 01:00:03;18, a widely used reference figure for the 23.976→29.97 pulldown offset.

The 23.976 ↔ 29.97 pulldown relationship

23.976 and 29.97 are not just "close" rates — they are linked by 2:3 pulldown: every 4 film frames (23.976) become 5 video frames (29.97), since 30 ÷ 24 = 5/4 exactly. Because pulldown preserves real time (the film does not speed up, it is just re-interlaced), 23.976 → 29.97 is always a same-moment conversion, never a conform. For the frame-by-frame field cadence, use the 2:3 Pulldown Cadence Diagram tool — this converter overlays a simplified cadence band on the target ruler whenever that rate pair is selected.

What 1 source hour becomes under conform

Each cell is source-hour-frames ÷ target rate, verified by direct division — there is no rounding involved for these integer rate pairs.

1. Enter the source timecode with its frame rate, then pick the rate you are going to.

2. Compare both answers side by side — same moment holds the real-world instant, conform holds the frame number.

3. Use the aligned rulers to read the sub-frame remainder, and trace 2:3 cadence on the pulldown diagram generator.