What Is 23.976 fps? Why '24 fps' Video Usually Isn't
Check your camera, your editing timeline, or the file a client just sent you, and odds are the “24 fps” footage is actually running at 23.976 frames per second. That missing 0.024 of a frame has caused more sync problems, failed QCs and 2 a.m. panics than almost anything else in post-production. Here’s the whole story in five minutes.
Where 23.976 comes from
Film runs at 24 fps. American NTSC television runs at 29.97 fps (slowed 0.1% from 30 when color TV arrived in 1953 — see our drop frame guide for that saga).
To broadcast film on NTSC television, engineers used 3:2 pulldown — spreading 4 film frames across 10 video fields. For the math to work perfectly, the film had to be slowed by the same 0.1% factor: 24 ÷ 1.001 = 23.976 fps.
Digital video inherited all of it. Cameras, editing systems and delivery specs kept 23.976 (often written “23.98”) so material stays compatible with the broadcast world. True 24.000 survives mainly in theatrical DCP delivery.
Does anyone actually see the difference?
No. A 0.1% speed difference is completely invisible — and inaudible (it’s a 1.7-cent pitch shift). The difference matters only to machines and math:
- Over an hour, 23.976 material runs 3.6 seconds longer than the same frame count at true 24.
- Timecode at 23.976 counts frames 00–23 as if it were 24 fps, so one “timecode hour” is not a real hour.
- Audio sync: mix a true-24 picture with a 23.976 workflow (or vice versa) and sound drifts about 1 frame every 42 seconds — sync at the head, noticeably off by the end of a reel.
The classic traps
Trap 1 — “It’s all 24, right?” A composer’s studio exports at true 24; the edit is 23.976. Everything lines up at the first cut and drifts from there. Always confirm the exact rate, in numbers, in writing.
Trap 2 — Subtitles from a different master. Subtitle files timed against a 25 fps (PAL) version drift progressively against a 23.976 master — about 4.3 seconds per hour. The fix is a frame-rate retime, which our subtitle sync tool does in one click.
Trap 3 — Duration math for deliveries. A “60-minute” program measured in 23.976 timecode is 60 minutes and 3.6 seconds of real time. When a platform specifies a maximum duration, know which clock they mean. Our timecode calculator shows the real running time next to every result for exactly this reason.
Which rate should you shoot?
- Web/streaming content: 23.976 is the safe default — it’s what platforms, cameras and NLEs expect.
- Theatrical DCP: true 24.000 (converting from 23.976 is trivial and standard).
- PAL-market broadcast: 25 fps, and none of this madness applies.
- Mixed delivery: shoot 23.976 and conform where needed; going 23.976 → 24 is a clean 0.1% speedup.
The rule that saves careers: never assume “24” means 24.000. Ask, verify in the file’s metadata, and make your whole pipeline agree on one number before the first cut.