Add and subtract SMPTE timecodes, convert timecode to frames or real duration, and switch between 23.976, 24, 25, 29.97 drop-frame and 60 fps — free, right in your browser.
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NTSC video does not run at an even 30 frames per second — it runs at 30000/1001 ≈ 29.97 fps. Non-drop timecode (NDF) still labels 30 frames every second, so the counter falls behind the wall clock: after one hour of real time, 29.97 NDF timecode reads only 00:59:56.4 worth of labels — a drift of 3.6 seconds per hour. That is fine for short-form work, but a broadcaster timing a program to the second cannot live with it.
Drop-frame timecode (DF) fixes the drift by renumbering, not by deleting video: it skips frame numbers 00 and 01 in the first second of every minute, except minutes divisible by ten (00, 10, 20, 30, 40, 50). That removes 2 labels × 54 minutes = 108 labels per hour, which keeps drop-frame timecode within 3.6 milliseconds of the wall clock over an hour. After 00:00:59;29 the next frame is 00:01:00;02 — frames ;00 and ;01 simply do not exist in that minute. No frames are dropped; only numbers are.
Conventions to remember: drop-frame is written with a semicolon before the frames field (01:00:00;00), non-drop with a colon (01:00:00:00). Drop-frame only exists for 29.97 (and 59.94) — there is no drop-frame at 24, 25 or true 30 fps, because those rates do not drift. NTSC broadcast masters are almost always 29.97 DF; PAL countries use 25 fps and never need it; film and digital cinema use 24 or 23.976.
| Frame rate | Typical use | 1 TC hour = frames | Real length of 1 TC hour |
|---|---|---|---|
| 23.976 fps | Film and episodic delivered into NTSC ecosystems | 86,400 | 1:00:03.600 |
| 24 fps | Film, digital cinema (DCP) | 86,400 | exactly 1:00:00 |
| 25 fps | PAL broadcast and online video in 50 Hz regions | 90,000 | exactly 1:00:00 |
| 29.97 fps DF | NTSC broadcast masters (wall-clock accurate) | 107,892 | 0:59:59.996 |
| 29.97 fps NDF | NTSC post, dailies, short-form | 108,000 | 1:00:03.600 |
| 30 fps | Web video, smartphones | 108,000 | exactly 1:00:00 |
| 50 fps | PAL high frame rate, sports | 180,000 | exactly 1:00:00 |
| 59.94 fps | NTSC high frame rate, sports | 216,000 | 1:00:03.600 |
| 60 fps | High-frame-rate web, gaming captures | 216,000 | exactly 1:00:00 |
A "TC hour" is one hour on the timecode counter (01:00:00:00). At fractional rates that is not one hour of real time — which is exactly why drop-frame exists, and why the TC ↔ duration tab above uses the exact 1001-based ratios instead of rounded frame rates.
Drop-frame is a counting scheme for 29.97 fps NTSC video. Because the picture really runs at 30000/1001 frames per second, labelling 30 frames every second lets the counter fall 3.6 seconds behind the clock each hour. Drop-frame skips frame numbers 00 and 01 at the start of every minute — except minutes ending in zero — so timecode stays wall-clock accurate. No frames are deleted, only numbers are skipped, and it is written with a semicolon: 01:00:00;00.
Black-and-white NTSC television ran at exactly 30 fps. When color arrived in 1953, the color subcarrier had to coexist with the existing audio carrier without interference on older sets, and the cleanest fix was slowing the frame rate by 0.1% — 30 × 1000/1001 ≈ 29.97 fps. Every NTSC-derived rate inherited that ratio, which is why 23.976 and 59.94 exist too.
86,400 frames — 24 frames × 3,600 seconds (coincidentally the number of seconds in a day). At 25 fps PAL an hour is 90,000 frames, at 30 fps it is 108,000, and one hour of 29.97 drop-frame timecode holds 107,892. The TC ↔ frames tab above gives the count for any timecode at any of the nine rates.
23.976 (precisely 24000/1001) is 24 fps slowed by 0.1% so film-originated material plays cleanly inside NTSC systems. The two look identical, but the same 86,400 frames last 3.6 seconds longer at 23.976 — enough to pull audio out of sync if a project mixes them up. Always confirm whether a delivery spec means true 24 or 23.976 before conforming.
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