What reading speed means here
In subtitling, reading speed is the rate at which text appears relative to how long it stays on screen. It is usually expressed as characters per second, or sometimes as words per minute. If a subtitle contains a lot of text and is on screen only briefly, the reading speed is high and many viewers will struggle to finish it. If the text is short and stays up longer, the speed is lower and easier to follow.
It is a property of the subtitle, not the viewer, but the limits set for it are based on what viewers can usually manage. Individuals differ widely, so no single figure suits everyone.
How it is calculated
The sum is simple: count the characters in the cue, then divide by the number of seconds the cue is displayed. Most guides count spaces and punctuation, and some count line breaks differently, so exact figures vary between tools.
A hypothetical example: a cue contains 68 characters and appears for 4 seconds. The speed is 68 divided by 4, which is 17 characters per second. If the same text were shown for only 3 seconds, the speed would be about 22.7 characters per second (68 divided by 3), which is noticeably harder to read.
Words per minute is a different way of expressing the same idea. Assume, purely for illustration, an average of about six characters per word including the space. At 17 characters per second, that is a little under three words per second, or roughly 170 words per minute (17 divided by 6, times 60). Real text varies a lot, so this is a rough conversion at best.
Typical limits
Guides commonly set a maximum, often in the mid-to-high teens of characters per second for adult audiences, and a lower one for children subtitles or for content aimed at less experienced readers. Some allow higher speeds in short bursts. These figures change with language, medium and client, and a number quoted by one guide is not a universal rule. If your project has a guide, use its figure.
What affects how fast people can read
- Age and reading experience. Children and some older viewers read more slowly. See also the notes on older viewers.
- Language. Reading a foreign language, or a second language, is slower than reading a first language. This matters for audiences who are language learners.
- Script and language structure. Characters carry different amounts of meaning in different writing systems, so character counts are not equivalent across languages.
- Text complexity. Familiar words and simple sentences are read faster than unusual names and technical terms.
- The picture. If the scene has a lot to look at, viewers spend less time on the text. A static shot leaves more attention for reading.
- The screen. Small, bright or distant screens slow reading; see font, size and contrast.
- Individual needs. Some viewers, including some neurodivergent viewers and people with learning disabilities, may need slower speeds or more time. Others read faster than average.
Why fast dialogue is hard to show
People can speak much faster than they can read. In fast conversation, rapid-fire exchanges or excited speech, a word-for-word transcript would exceed reasonable reading speed even with the full screen time available. When that happens, the writer has options.
- Condense the text. Trim the wording while keeping the meaning, as explained in the article on text condensation.
- Extend the cue. Let the subtitle stay up a bit longer, within the limits of the next cue and the scene. The related topic is display duration.
- Reduce overlap. Where speakers talk over each other, show the most important line rather than everything.
- Accept a short burst of higher speed. Where a guide allows it and the content is simple.
Cues also cannot be stretched forever. They must not run into the next one, and leaving enough gap between cues matters for readability, a subject covered in cue gaps. In practice the available time is limited by the speech and the scene. Subtitle timing as a whole is the framework within which reading speed sits.
Minimum and maximum durations
Reading speed works alongside rules for minimum and maximum display time. A very short word can still need a minimum time on screen to be noticed, while a long cue should not stay up so long that the viewer reads it twice and loses track of the scene. Typical guides set these limits in the range of about a second at the short end and several seconds at the long end, but the numbers vary.
Reading speed and accessibility
For viewers who are deaf or hard of hearing, subtitles or captions are often the only source of dialogue, so heavy condensing can mean lost information. Some services therefore aim to stay closer to the spoken wording, which raises the reading speed, and allow viewers more adjustment. There is a genuine tension here between giving all the words and keeping text readable, and different projects strike it differently. Offering a verbatim version alongside an edited one is one approach where resources allow.
What reading speed cannot tell you
Speed is a useful number, but it is only one measure. A subtitle at a comfortable 15 characters per second can still be difficult if the line breaks are awkward, the contrast is poor or the wording is unclear. Likewise, a briefly higher speed on a simple, familiar phrase may be fine. Reading speed is checked alongside other factors when judging subtitle quality, and most tools flag cues that exceed a set limit so a person can review them.
Practical tips
- Check the speed of every cue, not just the average.
- Review the fastest cues first; they are where problems cluster.
- Consider the audience: children, language learners and older viewers need more time.
- When a cue is too fast, try condensing before changing the limits.
- Test with real viewers where possible, since people read at very different rates.