Free tool
Timecode calculator
Add and subtract timecode, work out the duration between two points, and convert between timecode, frames and seconds. Drop frame handled properly at 29.97 and 59.94.
Only applies to 29.97 and 59.94
Adds one frame, the way a clip length is counted
Type in any box and the other two follow.
Timecode
00:00:00:00
What drop frame actually does
NTSC video runs at 29.97 frames per second, not 30, so a timecode counting 30 frames a second drifts ahead of the clock by about 3.6 seconds every hour. Drop frame fixes the count by skipping two frame numbers at the start of every minute except every tenth minute. No frames of video are lost, only numbers in the count. Drop frame timecode is written with a semicolon before the frames, like 01:00:00;00.
Why 23.976 has no drop frame
Drop frame exists to keep a 30 frame count honest against a 29.97 clock. At 23.976 the timecode counts 24 frames a second and simply runs slow against real time, which editors accept because the offset is predictable. That is why you will see 23.976 non drop and never 23.976 drop frame.
Counting a clip's length
A clip that runs from 01:00:00:00 to 01:00:10:00 is ten seconds long if you count the difference, and ten seconds plus one frame if you count both endpoints. Premiere shows durations the inclusive way. Use the inclusive toggle above when you are checking a clip length rather than a gap between two points.