Subtitle Line Count Estimator

Subtitle Line Count Estimator turns three numbers into a planning figure. Give it Video duration (seconds), a Reading speed (cps) and a Chars per line value, and it reports an estimated subtitle line count together with the arithmetic behind it, showing the character total it derived and how that was divided into lines.

It is built for people quoting work before the work exists. A project manager pricing a 90-minute documentary, a freelancer judging whether a rush job is feasible overnight, or an accessibility coordinator scoping a back catalogue all face the same question: roughly how much subtitle text is in this runtime? Waiting for a transcript is rarely an option when the quote is due today.

The model is simple and honest about being an estimate. Duration in seconds is multiplied by reading speed in characters per second to give a total character volume, and that total is divided by the characters-per-line figure and rounded up. Leaving Reading speed (cps) blank applies 17 cps, a common planning average for adult viewers; leaving Chars per line blank applies 38, comfortably inside the 42-character broadcast limit. The printed character total lets you audit the result rather than trust it blindly.

Because it assumes continuous speech, the figure is an upper bound for dialogue-light drama and closer to realistic for interviews, lectures and news. Everything recalculates instantly in your browser with nothing uploaded.

• Duration-driven estimate: Video duration (seconds) is the only value you truly have to supply, so a runtime from a media player is enough to produce a first scoping number.
• Adjustable reading speed: Reading speed (cps) lets you model your audience - lower for children's programming or a language that reads more slowly, higher for fast factual content - and defaults to 17 cps when left empty.
• Configurable line width: Chars per line reflects the house style you deliver to, defaulting to 38 characters, which sits safely under the common 42-character broadcast maximum.
• Shows its working: The result prints the derived character total alongside the line count and the values used, so a colleague or client can check the assumptions rather than argue with a bare number.
• Rounds up, never short: The line count is rounded up to a whole line, which keeps estimates conservative and avoids quoting a job as smaller than it will turn out to be.
• Instant what-if comparison: Change one input and re-run to see immediately how a different reading speed or line width moves the total, which is useful when comparing style guides.
• No file needed: Since it works from numbers alone, you can scope a job before any media or transcript has been delivered to you.

1. Get the runtime of the video in seconds - multiply minutes by 60 - and enter it in the Video duration (seconds) field, so a 45-minute episode is 2700.
2. Set Reading speed (cps) to the characters-per-second pace your audience can comfortably read, or leave it blank to use the 17 cps planning average.
3. Set Chars per line to your delivery style guide's line width, or leave it blank to use 38 characters, which stays under the usual 42-character ceiling.
4. Click Run and read the estimated subtitle line count, then check the bracketed breakdown underneath to confirm the character total looks sensible for the runtime.
5. Re-run with a slower reading speed to produce a low-end figure and a faster one for the high end, giving you a range rather than a single point estimate for the quote.
6. Adjust downward by judgement for material with long stretches of music, action or silence, since the calculation assumes speech throughout.
7. Copy the figures into your quote, or use the download button to save them as a .txt record of the assumptions behind the estimate.

Example 1 - scoping a ten-minute corporate video. Default assumptions give a quick baseline for a translation quote.

Video duration: 600
Reading speed:  17
Chars per line: 38

Estimated subtitle lines: 269
( 600s x 17 cps = 10200 chars, / 38 chars/line )

Example 2 - the same runtime for a children's audience. A slower reading speed and a shorter line reduce the character load but not the line count as much as you might expect, because narrower lines split the text further.

Video duration: 600
Reading speed:  12
Chars per line: 32

Estimated subtitle lines: 225
( 600s x 12 cps = 7200 chars, / 32 chars/line )

Running both gives you a defensible range to quote against, and the printed character totals are often more useful than the line count when a vendor prices per character.

• Quote before you have the media: A runtime alone is enough to produce a credible scope, so you can respond to an enquiry the same hour instead of waiting for files to arrive.
• More defensible pricing: Showing the character total and the assumptions behind it makes an estimate something a client can review, which heads off disputes when the final file lands.
• Better schedule planning: Knowing roughly how many lines a programme contains lets you convert it into translator hours and commit to a delivery date you can actually meet.
• Sensible defaults built in: The 17 cps and 38-character starting points reflect mainstream subtitling practice, so a first estimate is reasonable even without house figures of your own.
• Easy sensitivity testing: Re-running with different assumptions takes seconds and produces the high and low bounds that turn a guess into a considered range.
• Nothing to upload: The estimate is pure arithmetic performed in your browser, so no client material or project detail is transmitted anywhere.