Characters a second
Reading speed is the caption's characters, spaces included, divided by its seconds on screen. A 40-character caption shown for 2 seconds runs at 20 characters a second.
Caption reading speed calculator
Check whether a caption stays on screen long enough to read, against the 20 characters-a-second guideline.
- Free, no account
- Runs in your browser, nothing uploaded
Runs in your browser. Nothing is uploaded.
Result
Change any number and the answer updates.
Checking caption speed?
Studio keeps captions short and timed to your voice, on the video and on every clip.
00:20How it works
How to check a caption's reading speed
- Type the captionWith a line break where it wraps on screen.
- Type how long it is on screenIn seconds.
- Choose adults or childrenThe limit is 20 characters a second for adults and 17 for children.
00:30The details
What goes in and what comes out
- Privacy
- The sums run inside your browser. Nothing you type is sent anywhere.
- Cost
- Free. No account, no watermark, no trial that runs out.
00:35Worth knowing
Getting a good result
The limits used
They are the ones Netflix publishes for English subtitles: up to 20 characters a second for adult programmes and 17 for children's, at most 42 characters on a line, at most two lines, and between 5/6 of a second and 7 seconds on screen.
Two ways to fix a fast caption
Leave it on screen longer, if there is room before the next one. The answer shows the shortest time that works. Or cut words: captions do not have to carry every "you know" and "sort of".
00:40Questions
Caption reading speed calculator: common questions
Do spaces count?
Yes. Spaces and punctuation count as characters.
What about a whole caption file?
The readability checker runs this test on every caption in a file and can repair the timing.
Is 20 characters a second a rule?
It is a published style guide, not a law. Viewers who read slowly, and anyone watching in a second language, do better with less.
Is anything I type sent anywhere?
No. The sum is done by your browser.
What people do next
All planning toolsSubtitle readability checker
Check a caption file for lines that are too long, too fast, too short or overlapping, and fix them.
Subtitle editor
Fix caption text and timing line by line, with your video playing alongside.
Audio and video transcriber
Turn up to 5 minutes of speech into text and captions, in 17 languages, ready to copy or download.
Add subtitles to video
Burn an SRT or WebVTT caption file into a video so the captions show on every platform.
Skip the planning and send the recording.
Upload the raw recording. Studio cuts the ums, retakes and long pauses, adds captions and makes short clips. 30 free minutes, no card.