Described and Captioned Media Program / W3C WAI · reviewed 2026-10-10
What this source supports: Caption quality guidelines recommend keeping line length around 32 characters per line and reading speed below 180 words per minute for general content.
Source limit: Different content types (education vs children) use different timing targets.
These sources support the statements above. They do not show that every person needs this guide. They do not show a specific result.
Limits
This guide multiplies the rates you enter. It does not transcribe media or judge caption quality.
Different content types (education vs children) use different timing targets.
Use current instructions from the responsible organization. This guide is a planning aid, not an official decision or a substitute for qualified advice.
Common questions
What does the App compute?
Turn a media length, a speaking rate, and line limits into word, character, line, and cue counts.
What does the App not do?
This App multiplies the rates you enter. It does not transcribe media, write captions, or judge caption quality.
Where do the numbers come from?
You enter every number yourself. The sources support the method and the limits. They do not produce a result for your specific case. Keep the original documents next to the sheet you build.
Before you start
Open the linked source page and keep it beside you.
Gather the values the App asks for:
Running time in minutes.
Words spoken per minute.
Average characters per word.
Maximum characters per line.
Set aside ten quiet minutes; rushed numbers are the main error this guide prevents.
Free Companion App
The App computes the worked example with your own numbers, in your browser.
APP 1
Caption Transcript Word Budget
Turn a media length, a speaking rate, and line limits into word, character, line, and cue counts.
This guide is edited for clarity and checked against the sources it links. It is not a substitute for official instructions or qualified advice. A linked source does not show that every person needs this guide.