SyncMySubsSubtitle CPS & line-length checker
Characters per second (CPS) is how fast a viewer has to read a subtitle: its character count divided by how long it's on screen. Broadcast and streaming guidelines usually cap it around 17 to 20, with lines kept near 42 characters. This tool checks every cue against your limits, lists the ones that fail, and can safely re-wrap over-long lines. It all runs in your browser.
Reading speed and line length, at a glance
Subtitles have to be read at a glance while the picture keeps moving, so professional guidelines put limits on two things: how many characters appear per second, and how long each line is. Go over the CPS limit and viewers can't keep up; go over the line length and the text gets awkward or clipped. The usual numbers are roughly 17 to 20 CPS and about 42 characters a line, but they vary by broadcaster and audience, so both limits here are yours to set.
The checker measures every cue, counting the visible text without formatting tags, and lists each one that breaks a rule with its CPS and longest line. High CPS is a timing problem, not a line-break one, so the fix there is to give the cue more time with the Reading Speed tool. For over-long lines you can turn on re-wrap, which splits the text at spaces to fit the limit. It never changes a word, and it leaves cues with formatting tags untouched, so flagging always comes before any edit.
FAQ
What is CPS in subtitles?
CPS stands for characters per second: the number of characters in a cue divided by how long it stays on screen. It's a measure of reading speed. Broadcast and streaming guidelines usually cap it somewhere around 17 to 20 for adult programming, lower for children's content. A cue over the limit is on screen too briefly for its amount of text.
Why does line length matter?
Most guidelines keep each line to about 42 characters so a subtitle fits comfortably on screen and the eye can take it in without scanning too far. Longer lines can get cut off by a player or force an awkward wrap. Two lines of about 42 is the usual maximum.
Does the re-wrap change my words?
No. Re-wrap only moves the line breaks; it splits at spaces and never alters, adds, or removes a word. It also leaves cues that contain formatting tags alone, and it only touches lines that are over the limit. It can't lower CPS, which depends on timing rather than line breaks; for that, extend the duration with the Reading Speed tool.