Caption Reading Speed Calculator
Are your subtitles readable? Paste a caption and its on-screen duration to check characters-per-second, words-per-minute and line limits against the Netflix, TED and BBC standards.
Subtitle standards at a glance
Different platforms set slightly different reading-speed limits. These are the most widely used:
| Standard | Reading speed | Line limit |
|---|---|---|
| Netflix (adult) | 17 CPS | 42 chars × 2 lines |
| Netflix (children) | 13 CPS | 42 chars × 2 lines |
| TED | 21 CPS | 42 chars × 2 lines |
| BBC | ~160–180 wpm | 37–42 chars × 2 lines |
This tool flags ≤17 CPS as comfortable, up to 21 CPS as acceptable-but-fast, and anything higher as too fast to read.
How to fix captions that read too fast
- Trim the text. Condense to the essential words — captions don’t have to be word-for-word.
- Extend the duration. Hold the cue on screen a little longer, if the edit allows.
- Split the cue. Break one long caption into two shorter ones.
- Break lines sensibly. Keep lines to ~42 characters and break at natural phrase boundaries.
New to captioning? Read How to Add Captions & Subtitles to Videos, or size your script first with the Words to Time Calculator.
Frequently asked questions
What is a good reading speed for subtitles?
Around 17 characters per second (CPS) is comfortable for adults — the Netflix standard. Up to about 21 CPS (the TED limit) is acceptable but fast; beyond that, viewers can’t finish reading before the caption disappears.
How many characters per line should a subtitle have?
A maximum of about 42 characters per line, over no more than 2 lines, is the widely used standard (Netflix, TED). The BBC recommends 37–42. Shorter lines are easier to read at a glance.
How long should a subtitle stay on screen?
At least roughly 5/6 of a second (even for a single word) and no more than about 7 seconds. Too short and it can’t be read; too long and the eye re-reads it. The right duration depends on the text length and your target CPS.
How is characters per second (CPS) calculated?
CPS = total characters in the caption (including spaces) ÷ the time it’s on screen, in seconds. This calculator does it for you and flags whether you’re within comfortable reading limits.
Do captions help with SEO and engagement?
Yes. Captions make videos accessible, let the ~85% of social video watched on mute still land, and give search engines indexable text. They reliably lift watch time and reach — see our guide to adding captions.
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