Subtitle Frame Rate Converter

The Subtitle Frame Rate Converter retimes a SubRip file that was authored for one frame rate so it plays correctly on a video running at another. Paste the captions into the SRT Content box, enter the rate they were timed at in From fps and the rate of your target video in To fps, and every cue is rescaled by the ratio between the two. The corrected file downloads as .srt.

Frame-rate mismatch is the oldest sync problem in the business. Film runs at 24 fps, cinema transfers for NTSC territories at 23.976, PAL broadcast at 25, and NTSC video at 29.97. When a title crosses between those standards the running time changes, and a subtitle track timed to the original slowly walks away from the dialogue - imperceptible in the first minute, a second or more out by the end of the first act. Broadcasters, film distributors, localisation vendors and home-media authors all need a subtitle frame rate converter as a routine step in delivery.

The tool applies a single ratio: the target rate divided by the source rate. That factor multiplies both the start and the end of every cue, with the result rounded to the nearest millisecond. Going from 23.976 to 25 gives roughly 1.0427, so timings stretch; going the other way gives about 0.9591 and they compress. Because the correction is multiplicative rather than additive, cues near the start of the programme barely move while cues at the end move a great deal, which is exactly how frame-rate drift behaves. Both fields must contain a value or the tool asks for them; caption text, line breaks and ordering are never modified.

All processing is local to your browser, so nothing is uploaded and a full feature converts the moment you press Run.

• Ratio-based retiming: the scale factor is To fps divided by From fps, applied to both the in and out point of every cue, which is the mathematically correct correction for a standards conversion.
• Any rate you need: both fps fields take free numeric input, so 23.976, 24, 25, 29.97, 30 and less common rates are all supported rather than a fixed dropdown.
• Handles both directions: the same two fields cover film-to-PAL stretching and PAL-to-film compression without a separate mode.
• Text untouched: only timestamps are recalculated, so translated dialogue and deliberate line breaks survive the conversion intact.
• Guarded input: if either From fps or To fps is left blank the tool asks for both instead of returning a silently wrong file.
• Valid SubRip output: rescaled times are rounded to whole milliseconds and rewritten with the standard comma separator, ready for any player or validator.
• Instant and private: the convert subtitle fps online process runs in the page with no upload, no queue and no file limit.

1. Paste the subtitle file you need to retime into the SRT Content box, or click Load sample to see the effect on example cues.
2. Identify the frame rate the subtitles were originally timed to and type it into From fps - if a 23.976 fps source file has been supplied, enter 23.976.
3. Enter the frame rate of the video you are delivering against in To fps, such as 25 for a PAL master.
4. Press Run; every cue is multiplied by the ratio between the two rates and the corrected SubRip appears in the output.
5. Check the final cue against the end of your video, because frame-rate error accumulates and is largest at the tail of the programme.
6. Click Copy or Download to save the retimed .srt file.
7. If the video also has a different running time because of trims or added material, run the result through the sync corrector afterwards to handle that separately.

Example 1 - film to PAL. With From fps at 23.976 and To fps at 25, the scale factor is about 1.0427 and every timestamp stretches.

Before:
120
00:30:00,000 --> 00:30:03,000
We should have left an hour ago.

After:
120
00:31:16,860 --> 00:31:19,988
We should have left an hour ago.

Half an hour into the programme the cue has moved more than a minute - the drift a viewer experiences when a 23.976 subtitle is played against a 25 fps master.

Example 2 - PAL back to NTSC film. Set From fps to 25 and To fps to 23.976 and the factor becomes roughly 0.9591, compressing the same cue from 00:31:16,860 back to 00:30:00,000. The conversion is reversible, which makes it safe to experiment until the timing matches your picture.

• Delivers to broadcast spec: captions arrive at the correct frame rate for the territory and standard you are supplying, which is a normal condition of acceptance.
• Stops end-of-programme drift: the accumulating error that makes the final act unwatchable for caption users disappears in one pass.
• Reuses existing translations: a subtitle track already approved at one frame rate can serve another market without a new linguistic pass.
• Avoids costly redelivery: catching a frame-rate mismatch before QC does saves the turnaround, the re-encode and the awkward email.
• Reversible and low risk: because the operation is a simple ratio, converting back restores the original timing if you enter the wrong rate.
• Keeps masters confidential: the file never leaves your browser, so pre-release titles can be retimed without a transfer approval.