What are CPL and CPS?

For anyone making subtitles for their videos, CPS and CPL are very important. But what are they? Let us explain!

Maria Z avatar
Written by Maria Z
Updated over a week ago

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 of these 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 the CPS and CPL vary depending on the project?

CPS and CPL 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).

Moreover, the content of your video may necessitate a more flexible CPL and/or CPS. For example, if speakers are talking at a fast pace, it can prove very challenging to retain a CPS of 20. Sometimes even 25 is difficult to achieve.

While our standard Happy Scribe guidelines apply 42 CPL and 20 CPS, your own requirements may differ. We recommend to use Style Guides to specify your wishes for your content.

What counts as a 'character'?

A character is any single text you type in your caption. So any letter, number or symbol you use in your caption will be counted as a character.

For Japanese, Mandarin and Korean, a character means the same, though they contain a lot more content than e.g. a character from an alphabet.

Does that include spaces?

No, spaces are not counted as part of your CPS.

Where can I see my CPS and CPL on the Subtitle editor?

You can find them for each caption on the Text Editor section of the Subtitle editor.

Why is my CPS /CPL box in red?

If the CPS box is red, it means that your caption might not be readable for the viewer. You can try to shorten your caption or create a new one to split the text between two captions.

What does it mean if my CPS/CPL box is grey?

This means we believe that your caption is readable for your viewers. Nice work!

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