Frame Rate and Timecode Calculator
Convert a duration into a frame count at any frame rate, turn frames back into timecode, and see what changing the frame rate does to length.
Total frames
2,250
Timecode 00:01:30:00 at 25 fps. Editors count from frame zero, so the last frame is numbered 2,249.
This is what happens when a clip is conformed rather than re-timed: the frames are unchanged, so the length moves instead.
New duration
1:15
Speed change
120.0%
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Frames, seconds and timecode
Frame rate is how many still pictures make up a second of video. Multiply the rate by the duration and you have the frame count. Timecode is the same information written as hours, minutes, seconds and frames, which is how editors address an exact moment rather than an approximate one.
Frames are numbered from zero, so a clip with 250 frames runs from frame 0 to frame 249. Off-by-one errors here are a common source of a stray black frame at the end of an export.
Why 23.976 and 29.97 exist
These awkward numbers are a legacy of the switch to colour television in the NTSC regions. Adding colour information to a black and white signal required a small shift in the frame rate, and 30 became 30 divided by 1.001, which is 29.97. Film at 24 frames per second got the same treatment for the same reason, giving 23.976.
The practical effect is that a timeline running at 29.97 drifts against a real clock by about 3.6 seconds an hour. Drop frame timecode exists to hide that drift by skipping certain numbers in the count, never actual frames. It is a numbering trick, not a change to the video.
Conforming against re-timing
The second calculator above shows conforming: the frames are left exactly as they are and simply played at a different rate. Twenty-four frames played at 25 per second finish sooner, so the clip runs about four per cent short and everything in it moves four per cent faster, including the pitch of the audio if it is not corrected.
Re-timing is the other approach. The playback rate is fixed and frames are generated or discarded to fit, so the duration stays true. It keeps the timing honest at the cost of either duplicated frames, which judder, or interpolated ones, which can smear on fast motion.
Choosing a rate for new footage
Higher is not automatically better. Twenty-four frames per second carries a particular motion feel that audiences read as cinematic, largely because they have watched a century of film at that rate. Fifty or sixty is clearer on fast motion and is what most sport and gameplay uses. Shooting at a high rate and delivering at a low one gives you smooth slow motion; the reverse gives you nothing but a larger file.