Subtitle Characters per Line: Length and Line-Break Rules

These numbers aren't part of the SRT format — an SRT cue can hold one endless line. They come from style guides used by streaming platforms and broadcasters, and they exist so a viewer can read the subtitle in one glance without losing the picture. Here are the usual limits, the rules for where to break, and how to fix a file full of overlong lines.

How many characters per line?

• Spaces and punctuation count. “I'll be right back.” is 21 characters.
• These are maximums, not targets. A short line that fits is always better than a full one.
• The spec you deliver to wins. Some broadcasters use shorter lines, some older DVD specs allow a few more, and clients often have their own number.
• Vertical video needs less. A 9:16 frame is narrow; at a readable font size, a line that suits 16:9 will wrap. Many creators use much shorter lines, or one short line at a time.

Reading speed and duration

Line length is only half of readability; the other half is time on screen. For adult viewers, reading speed is commonly cited as about 17–20 characters per second in English-language guides, with lower limits for children's programmes. A full two-line English subtitle (around 84 characters) therefore needs four to five seconds. When a cue has more text than its duration allows, condense the wording — don't just make the lines longer.

Line-break rules

1. Keep it on one line if it fits

Bad:   I'll call you
       tomorrow.

Good:  I'll call you tomorrow.

2. Two lines should be similar in length (or bottom-heavy)

A long top line over one or two words looks like a mistake and makes the eye jump. When the lines can't be equal, many guides prefer the longer line at the bottom.

Bad:   I don't think we should tell your mother
       yet.

Good:  I don't think we should
       tell your mother yet.

3. Break after punctuation, at a natural phrase

Bad:   If you see Anna before Monday, tell
       her the keys are under the mat.

Good:  If you see Anna before Monday,
       tell her the keys are under the mat.

4. Don't end a line on an article, preposition or conjunction

Words like the, a, of, to, and, but belong with the words that follow them.

Bad:   She left the car at the
       station and walked home.

Good:  She left the car
       at the station and walked home.

5. Don't split names and fixed phrases

Bad:   We flew from Buenos
       Aires to Lima last night.

Good:  We flew from Buenos Aires
       to Lima last night.

6. Dialogue: one speaker per line, each with a dash

- Where are you going?
- Home.

Two speakers in one cue get one line each, whatever their length. Conventions differ on the dash (with or without a space, on both lines or only the second) — follow your style guide.

Why editors show “one long line + one word”

Import an SRT into Premiere Pro or CapCut and you sometimes get a full line with a stray word or two underneath. The cue in the file is a single line, just a little wider than the caption box, so the editor wraps only what doesn't fit. Machine-generated and translated subtitles are the usual source: they tend to come out as one long line per cue.

The fix is a hard line break in the file, at a good point, so the cue is two balanced lines everywhere. Two things to know about hard breaks:

• Widening the caption box doesn't re-join them. A line break is part of the text, so the cue stays on two lines however wide the box is.
• A narrower box can wrap them again. If each line is still wider than the box (vertical video, large font), each line wraps and the cue becomes three or four lines. Choose a line length that fits your smallest frame.

Split long subtitle lines automatically

Re-breaking hundreds of cues by hand is slow. The free subtitle line breaker does it in your browser — the file isn't uploaded.

The breaker follows the rules above: it prefers breaks after punctuation, avoids ending a line on an article or preposition, avoids splitting capitalized names, and never makes a cue three lines. Cue numbers and timecodes are copied exactly, so the timing doesn't change. Two-line dialogue cues (one speaker per line, with dashes) and cues that already have three or more lines are left as they are, and so are scripts written without spaces between words, such as Thai.

Keeping two-line subtitles in translation

Translation often flattens a carefully broken file: each cue is translated as one sentence and comes back as one long line. When you translate with SubtitleFlow, a source file that uses two-line subtitles keeps that layout: in a single-language SRT or VTT export, a translated cue whose source was two lines is split into two balanced lines when it is wider than your file's caption box, and dialogue cues get one line per speaker again. Bilingual exports keep one line per language instead, so a cue doesn't grow to four lines.

Frequently asked questions