Quick answer
Add the lengths in playback order. Each chapter starts at the sum of everything that plays before it.
Step by step
- List each clip in order with a consistent format such as minutes:seconds. Include intros, transitions and outros when they are part of the export.
- Start the first chapter at 0:00. Add its duration to find the next start, and repeat for each chapter.
- Add the final clip to find the full runtime. Compare your calculated starts with the exported video before publishing the chapter list.
Worked examples
Three clips
A 0:45 intro, 1:20 lesson and 0:30 wrap-up total 2:35. The chapter starts are 0:00, 0:45 and 2:05.
Trim a transition
If the exported lesson is shortened by 10 seconds, the wrap-up starts at 1:55 and the total becomes 2:25.
What to check
Label your source units. For long videos use hours:minutes:seconds consistently, and follow your publishing platform’s chapter format.
Related guides
Sources
See the calculation methodology or report an error.