CPL and CPS are the main indicators of your subtitles' readability. CPL stands for Characters Per Line and indicates how many characters are shown on screen per line of subtitles. CPS stands for Characters Per Second and indicates how many characters are shown on screen per second of video.
Why are they important?
The CPL determines how much space your audience has to read your subtitles.
The CPS indicates how much time your audience has to read your subtitles.
Both need to be at healthy amounts to make sure your subtitles are legible. Ideally, you want subtitles that take up a normal amount of space (max. 42 CPL) and a normal amount of time (max. 20 CPS).
Lower CPL and CPS are always better, though lots of little subtitle events (many events with low CPL) or subtitles that stay on screen for a very long time (one or multiple events with very low CPS) can also be distracting for a viewer.
Can CPL and CPS vary depending on the project?
CPL and CPS are not set in stone. They depend on:
The language (Japanese, Mandarin, and Korean have a CPL limit around 16–18 and a CPS that may be as low as 6).
The video orientation (portrait and square modes).
The service (closed captions for public TV use a 32 CPL limit).
The industry requirements (some industries need 17 CPS).
The content of your video can also play a role. If speakers are talking at a fast pace, keeping a CPS of 20 can be very challenging — sometimes even 25 is difficult to achieve.
While HappyScribe's standard guidelines apply 42 CPL and 20 CPS, your own requirements may differ. We recommend using Style Guides to specify your preferences for your content.
What counts as a character?
A character is any single unit of text you type in your caption — any letter, number, or symbol counts.
For Japanese, Mandarin, and Korean, a character means the same thing, though each character carries a lot more content than a single character from a standard alphabet.
Does that include spaces?
No, spaces are not counted as part of your CPS or CPL.
Where can I see my CPS and CPL in the Subtitle editor?
You can find them for each caption in the Text Editor section of the Subtitle editor. The number on the left of the timestamps represents the characters per second (c/s), and the number on the right represents the characters per line.
Why is there a red warning icon in my caption?
If the CPS number turns red and shows a triangle icon, it means the subtitle might be difficult for the viewer to read in time. You can try to shorten your caption or split the text across two captions:
What if there is a red number with a 'c'?
This means the characters per line (CPL) limit has been exceeded. Try shortening the line or splitting the caption to bring it back within range.
What does it mean if my CPS/CPL are grey?
Good news — grey means your caption is readable for your viewers.
If you have any questions about CPL, CPS, or the Subtitle editor, our Support team is happy to help at support@happyscribe.com.