Subtitle Reading Speed & Duration Calculator

How it works

cps = characters (incl. spaces) ÷ seconds; wpm = words ÷ seconds × 60; minimum duration = characters ÷ max cps (≥ 5/6 s); maximum characters = duration × max cps

Subtitles fail when viewers cannot finish reading them before they vanish, so every major guideline caps reading speed: Netflix at 20 characters a second for adults and 17 for children, broadcasters at 12–17, older recommendations at 160–180 words a minute. Characters per second, counting spaces, is the working measure because it is independent of word length and language; logographic scripts read at roughly half the character rate. The same rules cap a cue at two lines of 37–42 characters and between about 0.8 and 7 seconds, and ask for balanced lines broken at natural phrase boundaries. Meeting the speed limit almost always means condensing rather than stretching — cutting redundancy, fillers and repeated names — which is the core craft of subtitling; verbatim captions for accessibility trade some of that for completeness, hence their lower speed targets.

Worked example

Two lines totalling 87 characters and 18 words shown for 3.2 seconds read at 27 cps (338 wpm) — well over Netflix’s 20 cps. The cue needs at least 4.4 s on screen, or must be trimmed to 64 characters; the longest line (51) also exceeds the 42-character limit and should be re-broken.

Frequently asked questions