Subtitle Duration Calculator

The Subtitle Duration Calculator turns an SRT file into a readable timing sheet. Paste your captions into the SRT Content box, run it, and you get one row per cue with the cue number, exactly how long that caption stays on screen in seconds to two decimals, and the time range it covers. Nothing is altered; the result is a text report you can save with the .txt extension.

Display time is the quiet variable behind most readability complaints. A caption that flashes for a third of a second is unreadable however short the text, and one that sits for fifteen seconds usually means a cue that was never closed at a scene change. Subtitlers checking their own work, accessibility reviewers auditing a course, and editors receiving a file from an unfamiliar vendor all want duration as a list rather than by clicking cue by cue through a timeline.

The tool parses each SubRip block into start and end milliseconds, subtracts them and divides by 1000 for a two-decimal seconds figure. The range is printed back in standard HH:MM:SS,mmm form with an arrow between in and out point, so each row is self-describing and pastes straight into a QC note or spreadsheet. Cues appear in file order, numbered from the parsed list, and an empty or unparseable input returns a plain message rather than a blank page.

Because the analysis is read-only and runs in your browser, you can check a client's master without modifying it and without uploading a line of dialogue.

• Per-cue display time: Every subtitle in the SRT Content box gets its own row with an on-screen duration in seconds to two decimal places, so short and long outliers stand out immediately.
• Full time range shown: Each row repeats the start and end timecodes alongside the duration, letting you jump straight to the moment in your editor or player without cross-referencing the file.
• Sequential numbering: Rows are numbered in file order from the parsed cue list, so the report reads cleanly even if the source file had irregular indices.
• Completely read-only: The tool never rewrites timings or text, which makes it safe to run on a delivered master you are only meant to inspect.
• Plain text output: Results download with a .txt extension and paste neatly into QC notes, email or a spreadsheet column for further sorting.
• Clear empty-input handling: If nothing is pasted or no cues can be parsed, you get an explicit message rather than a confusing blank result.
• Single control, no setup: There is only the SRT Content box and the run action, so there is nothing to configure and nothing to get wrong.
• Local and instant: A full feature-length file is measured in the browser in a fraction of a second with no upload.

1. Paste the subtitle file you want to measure into the SRT Content box, or click Load sample if you want to see the report format before using your own captions.
2. Press Run to produce the duration list; there are no options to set because the tool reports on the file exactly as pasted.
3. Read down the seconds column looking for anything under roughly one second, since those cues will flash past before a viewer can finish them.
4. Look next for unusually long values, because a cue running well past seven or eight seconds is often a line that should be split or one whose end time was never trimmed.
5. Use the start and end timecodes printed on each flagged row to find that moment in your subtitle editor and correct the in or out point.
6. Copy the report or download it as a .txt file to attach to a QC note, and re-run after editing to confirm the outliers are gone.

Example 1 - spotting a flash frame. Cue 2 was clipped during an edit and now appears for barely a quarter of a second, which the report makes obvious next to its neighbours.

Per-cue display duration:
1. 3.00s  (00:00:01,000 -> 00:00:04,000)
2. 0.24s  (00:00:04,100 -> 00:00:04,340)
3. 2.50s  (00:00:05,000 -> 00:00:07,500)

Example 2 - an unclosed cue at a scene change. A caption whose out point was never trimmed sits on screen through the whole of the next shot.

7. 14.80s  (00:02:11,200 -> 00:02:26,000)
8. 2.10s   (00:02:26,500 -> 00:02:28,600)

Neither file is broken in a way a validator would catch, but both would draw viewer complaints, and a scan of the duration column finds them in seconds.

• Readability problems become visible: Seeing every display time as a list surfaces flash cues and stranded captions that are almost impossible to notice while watching at speed.
• Faster than clicking through an editor: One run replaces scrolling cue by cue through a timeline just to read the in and out points.
• Evidence for a QC note: The plain text report can be pasted directly into feedback to a vendor or translator, with cue numbers and timecodes already attached.
• Safe on files you must not change: Because it only reads, you can audit a delivered master without any risk of altering an approved deliverable.
• Supports accessibility standards: Adequate display time is a core requirement for usable captions, and measuring it is the first step to meeting it.
• Your content stays yours: The whole measurement happens in the browser, so no dialogue is ever transmitted.