Two different conversions
"Convert this timecode to another frame rate" can mean two things, and they give different answers. The converter shows both. It opens on a 90-minute timecode at 23.976 going to 25 fps.
Same moment in real time
The picture plays at its normal speed and you want the label of the same moment at the new rate. Use this to match a point between two versions of a project made at different rates, or to place a marker from a 25 fps edit on a 23.976 master. 01:30:00:00 at 23.976 is 1 h 30 min 5.4 s on the clock, which is 01:30:05:10 at 25 fps. The result is rounded to the nearest frame, because the two rates' frames do not line up exactly.
Same frames at the new speed
A conform keeps every frame and plays them at the new rate, so the running time changes and the timecode label of each frame changes with it. Playing that 23.976 film at 25 fps runs it 4.27% faster: the same frames end at 01:26:24:00 and the film lasts 1 h 26 min 24 s. Sound has to be sped up by the same amount, usually with pitch correction.
Speed changes for common conforms
| From | To | Speed | A 90-minute programme becomes |
|---|---|---|---|
| 23.976 | 24 | +0.10% | 1 h 30 min 0 s |
| 23.976 | 25 | +4.27% | 1 h 26 min 24 s |
| 24 | 25 | +4.17% | 1 h 26 min 24 s |
| 25 | 24 | −4.00% | 1 h 33 min 45 s |
| 25 | 23.976 | −4.10% | 1 h 33 min 50.625 s |
| 29.97 | 30 | +0.10% | 1 h 30 min 0 s |
The first column is the programme's own rate. Its length is measured by its timecode, 01:30:00:00, so the 23.976 and 29.97 rows start from 1 h 30 min 5.4 s of real time.
Drop-frame and non-drop at the same rate
Choosing 29.97 DF and 29.97 NDF (or 59.94 DF and NDF) keeps the speed the same and only relabels the frames. The "same frames" answer is the other label for the same frame: 01:00:00:00 non-drop is 01:00:03;18 drop-frame. The drop-frame calculator explains why.
What this does not do
Moving 23.976 material into a 29.97 timeline without changing speed usually means 2:3 pulldown, which repeats fields rather than mapping one frame to one frame. The real-time answer still tells you where a moment lands, but frame-accurate pulldown cadence is a job for your editing software.
For plain timecode math, use the main timecode calculator or the frames to timecode converter.
Questions
How do I convert timecode from 23.976 to 25 fps?
Decide whether the picture keeps its speed or is conformed. At the same speed, take the real time of the timecode and find that moment at 25 fps. In a conform every frame keeps its number and plays 4.27% faster, so the timecode of each frame changes. The converter shows both.
What is the speed change from 24 to 25 fps?
4.17% faster, so a 90-minute film becomes 1 h 26 min 24 s. From 23.976 to 25 it is 4.27% faster.
Why is the real-time result rounded?
Frames at two different rates rarely start at exactly the same instant, so the converter picks the frame nearest to the same clock time.
Can I convert drop-frame to non-drop timecode?
Yes. Pick 29.97 DF as the starting rate and 29.97 NDF as the target. The speed stays the same and the result gives the other label for the same frame.