SMPTE timecode counts in hours, minutes, seconds and frames — and frames are not decimal. Adding 00:00:45:20 to 00:00:30:15 at 25 fps does not give 00:01:15:35, because there is no frame 35 in a 25 fps second. This calculator handles the carry for you, at any frame rate, and converts a duration from one frame rate to another without you having to reach for a pen.
Use it to work out the length of a segment, to find the difference between an in-point and an out-point, to add a handle to a clip, or to translate a running order written at 25 fps into the 29.97 fps world of a co-production.
NTSC video does not run at 30 frames per second. It runs at 30 ÷ 1.001, which is 29.97. Over an hour, a counter that ticks 30 frames per second drifts ahead of the wall clock by 3 seconds and 18 frames.
Drop frame timecode fixes this by skipping two frame numbers — not two frames of picture — at the start of every minute, except every tenth minute. Nothing is removed from the video: only the labels change, so that after one hour of real time the counter reads 01:00:00:00. Drop frame is written with semicolons (01:00:00;00) and is what you use when the timecode has to match the broadcast clock.
Non-drop frame counts every frame number in sequence. It is simpler, it is what you want in the edit suite when you care about frame counts rather than duration, and it will slowly disagree with the clock on the wall. It is written with colons (01:00:00:00).
The rule of thumb: drop frame for transmission, non-drop frame for post-production. Get this wrong on a one-hour programme and you are 3.6 seconds out — enough to miss a junction.
When you convert a timecode from one frame rate to another there are two different questions, and they have different answers.
Most mistakes in a machine room come from confusing these two. The calculator shows both, so you can see which one you actually meant.
A timecode counter tells you where you are inside a recording. It does not tell you what time it is. In a broadcast facility those two have to agree, and keeping them in agreement is a hardware job: a reference clock disciplined by GNSS or by a network time source, distributed to every device that needs it.
That is what we build. If you are running this calculator because a timecode somewhere is drifting away from the clock, the calculator will tell you by how much — but it will not fix it.
These tools are free because we build the equipment that does the same job in a control room, twenty-four hours a day, without a browser tab open.
Elettronica Mangione has been designing broadcast synchronisation systems in Rome since 1984, with over 1,000 installations in 15 countries. Talk to a timing engineer.
Drop frame skips two frame numbers at the start of every minute except every tenth minute, so that the counter keeps pace with real time on 29.97 fps NTSC video. Non-drop frame counts every frame in sequence and drifts ahead of the wall clock by about 3.6 seconds per hour. Drop frame is written with semicolons, non-drop frame with colons.
Enter both values, choose the frame rate, and select the add operation. The calculator carries frames into seconds, seconds into minutes and minutes into hours according to the frame rate you selected, which is where manual arithmetic usually goes wrong.
No. The calculator works on the numbers only. Converting 25 fps to 29.97 fps here tells you what the new timecode reads; it does not perform a standards conversion on any media.
Because non-drop frame counts 30 frames per second while the video actually runs at 29.97. After 01:00:00:00 of non-drop frame timecode, 60 minutes and 3.6 seconds of real time have elapsed.
25 fps, which is the PAL standard and does not need drop frame at all, because 25 is an exact number of frames per second.
Yes, and there is no registration. It runs entirely in your browser: nothing you type is sent anywhere.