How to check caption reading speed
- Drop your SRT, VTT or SBV file.
- Choose the rules (Netflix, BBC, US broadcast or your own).
- Read the summary; the table lists every subtitle that breaks a rule.
- Download the report as CSV if you need it.
How fast is too fast?
Reading speed is measured in characters per second (cps): the letters, spaces and punctuation of a subtitle divided by how long it stays on screen. Netflix allows up to 20 cps for English adult programmes and 17 for children's; the BBC works to about 160 to 180 words a minute. Above that, viewers stop reading and miss the picture.
The other checks
- Characters per line: 42 for Netflix, 37 for the BBC, 32 for US broadcast (CEA-608) captions.
- Lines: two at most.
- Duration: at least 5/6 of a second (20 frames), and no more than 7 seconds.
Captions for accessibility (ADA, WCAG)
WCAG 2.1 asks that captions are synchronized and accurate; the US Department of Justice's ADA Title II rule requires WCAG 2.1 AA from state and local governments. Readable captions are part of that: see the caption compliance checklist.
To fix every problem at once (re-wrapping lines, borrowing time from gaps), open the file in the CadreScripts editor: Captions → Checks → Fix all.
Questions
What is a good reading speed for subtitles?
For adults, up to 17 to 20 characters per second (about 160 to 200 words a minute); for children, 13 to 17. Netflix uses 20 cps for English adult programmes and 17 for children's.
How are characters per second counted?
All characters of the subtitle, spaces and punctuation included, with the two lines joined, divided by the time from its start to its end.
What is the maximum line length?
42 characters for Netflix, about 37 for the BBC, and 32 for US broadcast (CEA-608) captions. Two lines at most.
Does this fix the subtitles?
It reports the problems. The CadreScripts editor fixes them: it re-wraps lines and extends or joins subtitles while keeping them with the speech.