CPS
Characters per second
The reading-speed metric used by professional subtitle standards. Total characters in a cue divided by its duration in seconds.
In depth
CPS (characters per second) measures how fast a viewer must read a caption. It's calculated as the total visible character count of a cue divided by its duration in seconds. Spaces typically count; newlines don't. Lower CPS is more comfortable; higher CPS forces viewers to read past their natural speed and miss content.
When to use it
Use CPS when authoring or QA-ing subtitles for broadcast, streaming, or accessibility. Most professional workflows lint CPS before delivery.
Frequently asked
What's a good CPS for subtitles?+
Netflix caps adult English content at 17 CPS. The BBC uses 15 CPS for adult viewers. Children's content typically caps at 12. Short-form social video (TikTok, Reels) can push to 20 because viewers expect a faster pace and can re-read.
Why CPS instead of WPM?+
Word lengths vary across languages and registers. CPS gives a more reliable measure of reading load. WPM is still useful as a sanity check.
Do spaces count toward CPS?+
Yes — every visible character including spaces counts. This matches Netflix and BBC convention.
Reading speed expressed in words per minute. Easier to intuit than CPS but less consistent across languages.
The most common subtitle file format. Plain text with numbered cues and HH:MM:SS,mmm timestamps.
The W3C web standard for subtitles. Used by HTML5 <track> elements. Like SRT but with dot-separated milliseconds and styling support.