BYTETOOLS

Subtitle Reading Speed Checker

Check characters per second, words per minute, line length and gaps in any SRT or VTT file, then export retimed subtitles. Runs entirely in your browser.

Paste a subtitle file above (or load the sample) to see characters per second, words per minute, line lengths and gap warnings for every cue.

Defaults follow widely used broadcast and streaming practice — 17 characters per second for adult programming, 13 for children's, a minimum of about 5/6 of a second per subtitle and a maximum around six seconds — but every broadcaster publishes its own spec, so all limits above are editable. Parsing and retiming happen entirely in your browser.

What is the Subtitle Reading Speed Checker?

Subtitle Reading Speed Checker parses a pasted SRT or WebVTT file and measures every cue the way a subtitle QC pass does: characters per second, words per minute, cue duration, characters on the longest line, number of lines, and the gap to the next cue.

  • Reads both SubRip (.srt) and WebVTT (.vtt), including cue settings and inline tags
  • Per-cue characters per second, words per minute, duration and longest line
  • Editable CPS, minimum and maximum duration, minimum gap, line length and line count
  • Reading-speed distribution across five bands so you can see the whole file at a glance
  • One-click corrected SRT export that never overlaps cues or exceeds the maximum duration

How to use the Subtitle Reading Speed Checker

  1. 1

    Paste the contents of your .srt or .vtt file into the text box, or click “Load sample cues” to see how it works.

  2. 2

    Pick a reading-speed preset or type your own characters-per-second limit.

  3. 3

    Adjust the minimum and maximum duration, minimum gap, characters per line and lines per cue to match your delivery spec.

  4. 4

    Read the distribution bars and the cue-by-cue table — flagged rows are highlighted with the reason.

  5. 5

    Copy or download the corrected SRT, where every cue is extended just enough to hit your limits without overlapping the next one.

About the Subtitle Reading Speed Checker

Subtitle Reading Speed Checker parses a pasted SRT or WebVTT file and measures every cue the way a subtitle QC pass does: characters per second, words per minute, cue duration, characters on the longest line, number of lines, and the gap to the next cue. Anything outside your limits is flagged with the exact reason.

It is built for subtitlers, captioners, localisation QC staff and video editors who need to know whether a file will actually be readable before it goes to review. Reading-speed limits differ by broadcaster, so every threshold on the page is editable, with presets for the common 17 CPS adult and 13 CPS children's figures.

Parsing, measuring and retiming all happen locally in your browser — your subtitle file is never uploaded, and the corrected SRT is generated on your own device.

Frequently asked questions

What is a good characters-per-second rate for subtitles?

Most streaming and broadcast specs sit around 17 characters per second for adult programming and about 13 for children's. Twenty CPS is usually treated as an absolute ceiling. The tool defaults to 17 but every limit is editable because each broadcaster publishes its own figure.

How is characters per second calculated?

It is the number of characters in the cue divided by the cue's duration in seconds. Line breaks are not counted, and you can choose whether spaces count as characters — some specs include them and some do not, which changes the result by roughly fifteen per cent.

What is the six-second rule?

It is the classic guideline that a full two-line subtitle of about seventy characters should stay on screen for six seconds, which works out at roughly twelve characters per second. Set the preset to “Six-second rule” to check a file against that older, slower standard.

Does the corrected export ever change my in-points?

No. Start times are left exactly as they are. Each cue's end time is extended only as far as your reading-speed and minimum-duration settings need, capped by the maximum duration and by the next cue's in-point minus your minimum gap.

Why are some cues still over the limit after correction?

Because there was no room to extend them — the next cue starts too soon, or the maximum duration was reached. Those cues need the text shortened or split across two subtitles, which is an editorial decision the tool leaves to you.

Is my subtitle file uploaded anywhere?

No. The file is parsed by JavaScript in your browser and never leaves your device. The page keeps working offline once it has loaded.

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