Check Subtitle Reading Speed
Or paste subtitle text
Options
The limit is not a number you type in: it is read out of a published document, and the report names that document, quotes the sentence it came from, says whether that sentence is a requirement or guidance, and gives the day we last verified it with a link. Pick the document you are answerable to. They do not agree with each other: Netflix counts characters per second and caps a line at 42 characters, while Ofcom and the BBC count words per minute and, on line length, the BBC caps a line at 37. Three of them state no figures at all — 47 CFR §79.1, WCAG 2.2 SC 1.2.2 and EN 301 549, which requires web pages and non-web documents to satisfy that same criterion. Those three require captions to identify who is speaking and to carry non-speech information, and leave every number to the broadcaster; a page that checks them asks whether the file does it, not whether some number is exceeded. They also do not carry the same weight: a defect that reads as a warning against WCAG reads as an error against EN 301 549, because the standard turns that criterion into a shall. Changing this box changes the limit and the citation together, so a report can never carry one document's number under another document's name. Pages that check something only one of these documents states offer only that one.
Which frame rate the timings are counted in. On the format pages this is what MicroDVD needs, because it stores timing as frame numbers. On the frame rate pages it is the rate the file was timed against — the version the subtitles were made for — and the page's second box takes the rate of the video you are going to use them with. 23.976, 24, 25, 29.97, 30, 50, 59.94 and 60 are the common ones. Getting it wrong shifts the whole timeline, and on the frame rate pages it shifts it by a ratio rather than by a fixed amount.
Reading speed is how fast a viewer has to read a cue. This page measures every cue in a subtitle file against the reading-speed limit in a standard you choose, and lists the ones that ask for more than that limit allows. Everything runs in your browser: the file is never uploaded, it is not changed, and what comes back is a report you can download as a PDF, or as a CSV to sort in a spreadsheet.
The limit is not a number you type in. It is read out of a published document, and the report prints which document, the sentence the number was read from, whether that sentence is a requirement or guidance, and the day we last verified it, with a link. Reading speed is stated in two different units, and this page keeps them apart instead of converting between them: Ofcom and the BBC state a limit in words per minute, Netflix states one in characters per second. A word is not a fixed number of characters, so a converted figure would be invented rather than quoted. Pick the standard whose unit matches the document you are answerable to.
What the page cannot decide matters as much as what it can. A file written without spaces between words — Chinese or Japanese subtitles — cannot be measured in words per minute at all, because counting words by whitespace counts the wrong thing, and the report says so instead of returning a figure that looks like an answer. And a report is a statement about a file, not about a service: the documents behind these numbers are written for broadcasters and streaming platforms, and how far they bind you is a question about your obligations rather than about your subtitles.
Examples
Two cues over Ofcom's 180 words per minute
Subtitles
1
00:00:01,000 --> 00:00:02,000
Where were you last night?
2
00:00:03,000 --> 00:00:07,000
I was working late, and I did not think you would notice.
3
00:00:08,000 --> 00:00:09,000
Every night this week?
What the report finds
Cues read faster than the limit — 2 found
Severity Cues Start End Measured Limit Clause
Warning 1 00:00:01.000 00:00:02.000 300 wpm 180 wpm Ofcom: Guidelines on the provision of television access services — Reading speed: subtitles should not exceed 160–180 words per minute
Warning 3 00:00:08.000 00:00:09.000 240 wpm 180 wpm Ofcom: Guidelines on the provision of television access services — Reading speed: subtitles should not exceed 160–180 words per minute
Checked against
Standard: Ofcom access services guidance
Limit: 180 wpm
Where it is stated: Reading speed: subtitles should not exceed 160–180 words per minute
Stated as: GuidelineThe first cue is five words held for one second, so it has to be read at 300 words per minute; the third is four words in one second, 240. The middle cue is twelve words held for four seconds, exactly 180, and is not reported. A short cue carrying a few words is often the fastest thing in a file, and each cue is measured from its own text and its own screen time.
Exactly on Netflix's 20 characters per second
Subtitles
1
00:00:01,000 --> 00:00:03,000
We can talk about it all in the morning.
What the report finds
Cues read faster than the limit — Nothing found.
Checked against
Standard: Netflix Timed Text Style Guide
Limit: 20 CPS
Where it is stated: Reading speed: 20 characters per second for adult content (17 for children's)
Stated as: Guideline
Not checked by this page: Duration: minimum duration 5/6 second (20 frames at 24fps); Duration: maximum duration 7 seconds; Line length: maximum 42 characters per line (43–44 only in rare exceptions); Line length: maximum 2 lines per subtitle eventForty characters, two seconds on screen, 20.0 characters per second against a limit of 20. Nothing is reported, because a cue sitting exactly on the limit is inside it, and the basis section still prints the limit and where it came from — a report that only said nothing was found would not tell you what it looked at.
A file whose words cannot be counted
Subtitles
1
00:00:01,000 --> 00:00:02,000
你到哪里去了？
2
00:00:03,000 --> 00:00:05,000
我昨天晚上一直在加班。
What the report finds
Cues read faster than the limit — Not applicable. No per-minute rate can be measured here: either the file holds no words at all, or its text is written without spaces between words (Chinese, Japanese), where counting words by whitespace counts the wrong thing. A characters-per-second standard measures a file like this one.
Checked against
Standard: Ofcom access services guidance
Limit: 180 wpm
Where it is stated: Reading speed: subtitles should not exceed 160–180 words per minute
Stated as: GuidelineTwo Chinese cues. Chinese is written without spaces between words, so splitting on whitespace would count each cue as a single word and hand back a comfortable reading speed — a pass that means nothing. The check refuses to produce that number and says why instead. The same file is measured properly under Netflix, whose limit is per character and therefore independent of how the language is written.
Frequently asked questions
How is a cue's reading speed worked out on this page?
Characters per second is the cue's character count divided by how many seconds it is on screen; words per minute is its word count divided by the same time in minutes. The character count includes spaces and punctuation, because that is how the Netflix style guide defines it, and excludes styling markup, so an italic line in an ASS file measures the same as the same words in an SRT file. The word count splits on whitespace and nothing else. Which one is used follows the standard you pick: Netflix states a limit per character, Ofcom and the BBC per word.
Why not convert between words per minute and characters per second?
Because the conversion needs an assumption about how long the average word is, and any figure produced that way is invented rather than quoted. The documents that state a limit in words per minute are checked in words per minute; the one that states a limit per character is checked per character. A converted limit would put a number in the report that appears nowhere in the document the report names.
Which documents can the reading-speed limit be read from here?
Three. Ofcom's guidelines on the provision of television access services and the BBC's subtitle guidelines both state 160 to 180 words per minute, and the Netflix Timed Text Style Guide states 20 characters per second for adult content and 17 for children's. All three are guidance rather than regulation, and the report labels them that way in a row of its own. The children's figure of 17 is not selectable here; this page checks the adult limit of 20.
Why does the report have nothing to say about my Chinese subtitle file?
It says something, and the something is that the check does not apply: no per-minute rate can be measured in a file whose text has no spaces between words, so counting words by whitespace would count each cue as a single word. Switch the standard to Netflix and the same file is measured in characters per second, which does not depend on how the language is written.
Does checking reading speed change my subtitle file?
No. The file is read and measured, and the report is the only thing produced; the original is untouched and nothing is uploaded. If you want the cues actually shortened, that is a different tool that writes a new subtitle file. This page tells you which cues are over the limit, not what to cut.
What does the reading speed report contain?
A header naming the file, its format, how many cues it holds and what was lost while it was read; one row per cue over the limit with the cue number, its start and end, the rate it measured and the limit it was compared against; and a basis section naming the document, the sentence, whether that sentence is a requirement or guidance, the day it was verified and a link to it, followed by the limits in that document this page did not check.
Is a cue that sits exactly on the reading-speed limit reported?
No. The comparison is strictly greater than the limit, so a cue measured at exactly 20.0 characters per second against a limit of 20 is inside it and is not listed. The same care runs the other way on the minimum-duration pages, where a cue exactly on the limit is also fine. A comparison written the wrong way round either flags every correctly timed cue in a file or passes one that breaks the rule, so both boundaries are pinned by their own example.
What the check looks for
- The report is a statement about a file; the documents it quotes are addressed to services. Ofcom's guidance applies to licensed television and on-demand services in the UK, the BBC's guidelines to BBC output, and the Netflix style guide is a delivery requirement in Netflix's supplier contracts. Nothing here says your subtitles satisfy any of them. It says which cues measured above which published limit, and which of that document's limits this page did not check.
- Reading speed carries more weight than it used to. The European Accessibility Act has applied since 28 June 2025, and in the United States the FCC has required captions to be displayed at a speed that permits them to be read since 2014. In both cases the duty falls on the service rather than on the file, and a measurement of your subtitles is one input towards meeting it, not evidence that you have.
References
- Ofcom: Guidelines on the provision of television access services — reading speed should not exceed 160 to 180 words per minute.
- Netflix Timed Text Style Guide — 20 characters per second for adult content, 17 for children's.
- BBC Subtitle Guidelines — reading speed 160 to 180 words per minute.
- 47 CFR §79.1(j)(2) — captions must be accurate, synchronous, complete and appropriately placed. The rule names no reading-speed figure, and this page does not check against it.