Subtitle standards
Subtitle reading speed (CPS) & line length
Last updated: 2026-06-11
A comfortable subtitle reading speed is about 15-20 characters per second (CPS): Netflix caps adult content at 17 CPS and children's content at 13 CPS. Lines should be no more than 42 characters each, with a maximum of two lines, an on-screen minimum near 0.83 s, and a maximum around 6 s before a cue is split. These limits keep text readable in the time the audio allows.
Reading speed, line length, line count, and duration are linked: a cue's CPS is its character count divided by its duration, so the same words become harder to read if the cue is short. The timecodes set the time available, which is why they should not change during translation.
Reading speed by standard
Different publishers set slightly different CPS ceilings, lower for children who read more slowly. The table lists common reference figures.
| Standard | Adult CPS | Children CPS |
|---|---|---|
| Netflix | 17 | 13 |
| General comfortable range | 15-20 | ~12-13 |
| BBC (approx.) | ~16-20 | lower |
| Hard ceiling (avoid above) | ~20-25 | ~17 |
Line length and line count
A subtitle line should not exceed 42 characters on Netflix (the BBC uses about 37-40), counting spaces and punctuation. Use at most two lines; a single line is preferred whenever the text fits, and a third line is avoided because it covers too much of the picture. When a line would overflow, break it at a natural grammatical point — after punctuation or before a conjunction — rather than mid-phrase, so each line reads as a coherent unit.
Duration limits
A cue needs enough time to be read but not so long it lingers. The minimum is about 0.83 s (commonly 20 frames at 24 fps) so the eye can register it; the maximum for a two-line cue is around 6 s, after which it should be split. A common working window is 5-7 seconds for two full lines. These durations interact with CPS: a long line shown too briefly blows past the reading-speed limit, while padding a short line out for 6 seconds wastes screen time.
| Limit | Value | Note |
|---|---|---|
| Min duration | ~0.83 s | 20 frames @ 24 fps |
| Max duration (2 lines) | ~6 s | Split if longer |
| Max chars/line | 42 | Netflix |
| Max lines | 2 | 1 preferred |
How to calculate CPS
Divide the cue's character count (including spaces) by its duration in seconds. A cue reading "I never said that to him" is 25 characters; shown for 1.5 seconds that is 25 ÷ 1.5 ≈ 16.7 CPS, within the comfortable range. Stretch the same line to only 1 second and it jumps to 25 CPS, too fast. Subtitle editors compute CPS automatically and flag cues over the threshold, but the math is simple enough to check by hand.
Reading speed and translation
Translation is where reading speed most often breaks. The timecode keeps the same duration, but languages like German or Spanish can run 20-30% longer than English, raising CPS for the same on-screen window. The fix is to condense the wording, never to stretch the timecode, because the timing is anchored to the audio. The SubLingo translator preserves every timecode exactly (see how to translate an SRT file); after translating, review the densest cues against the 17 CPS target. The underlying timing rules are covered in subtitle timecodes explained.
Key facts
- Comfortable reading speed: 15-20 CPS.
- Netflix caps adult at 17 CPS, kids at 13 CPS.
- Max line length 42 characters (Netflix); two lines maximum.
- Min duration ~0.83 s; max ~6 s for a two-line cue.
- CPS = characters ÷ on-screen seconds.
- Translation can raise CPS; condense wording, keep timecodes fixed.
Definitions
- CPS
- Characters per second — subtitle character count divided by on-screen duration. Measures reading speed.
- WPM
- Words per minute, an older reading-speed measure; roughly 160-180 WPM maps to comfortable CPS ranges.
- Line length
- Characters per line including spaces. Netflix caps it at 42; the BBC at about 37-40.
- Minimum duration
- Shortest time a cue stays on screen, about
0.83 s(20 frames at 24 fps). - Maximum duration
- Longest a single cue should stay up, around
6 s, before it is split. - Safe area
- The screen region where text won't be cropped; line length stays within it.
Related guides
FAQ
What is a good subtitle reading speed in CPS?+
A comfortable reading speed for adult viewers is about 15-20 characters per second (CPS). Netflix caps adult content at 17 CPS and children's content at 13 CPS. Higher than ~20 CPS forces viewers to read faster than they can comfortably keep up.
What is the maximum characters per line for subtitles?+
Netflix and most broadcast standards cap a subtitle line at 42 characters, including spaces. The BBC allows up to 37-40 characters per line. Staying within the limit keeps text from wrapping awkwardly or running off the safe area.
How many lines can a subtitle have?+
Two lines is the maximum for nearly all standards. A single line is preferred when the text fits, and a third line is avoided because it covers too much of the picture and is hard to read in the time available.
What is the minimum and maximum duration for a subtitle?+
The minimum on-screen duration is about 0.83 seconds (often given as 20 frames at 24 fps) so a viewer can register the cue. The maximum is around 6 seconds for a two-line subtitle, after which it should be split, with 5-7 seconds a common ceiling.
What does CPS mean?+
CPS means characters per second. It is the subtitle's character count divided by how long it stays on screen, and it measures reading speed. A 51-character cue shown for 3 seconds is 17 CPS. Lower CPS is easier to read.
Why do translations sometimes exceed the reading-speed limit?+
Some languages expand: a phrase that is short in English can be longer in German or Spanish, pushing CPS over the limit for the same on-screen time. Subtitlers then condense the wording, since the timecodes are fixed by the audio and should not change.
Does translation change reading speed?+
It can. The timecode keeps the same duration, but a longer translated line raises CPS. SubLingo preserves the timecodes exactly; if a target language runs long, review the densest cues and tighten the wording to stay readable.