Good subtitles are not only correct, they are readable in the time they stay on screen. Professional subtitlers follow a few simple limits; use them whether you write subtitles by hand or edit AI ones.
Line length
- At most 2 lines per subtitle.
- About 37 to 42 characters per line (Latin scripts). Shorter for vertical video.
- Break lines at natural points: after punctuation, before “and”, “but”, “because”, not between an article and its noun.
Reading speed
- Measured in characters per second (CPS).
- Around 15 to 17 CPS for adults, lower (about 13) for children’s content.
- If a subtitle is too fast, shorten the text rather than cramming it.
Duration
- Minimum about 1 second, even for “Yes”.
- Maximum about 6 to 7 seconds; longer subtitles get read twice.
- Leave a tiny gap between subtitles so the eye sees the change, and never let them overlap.
Translations get longer
German, French or Spanish often take 20 to 30% more characters than English. After translating subtitles, check the long lines and condense them.
Where to edit
Subtitle Studio lets you change text and timing next to the video and download SRT, VTT or TXT.