Subtitle Frame Rate Converter
Convert subtitle timestamps between 23.976, 24.0, 25.0, 29.97, and 60 fps. Fix progressive PAL/NTSC audio desync directly in your browser.
Drop your subtitle file to recalculate frame timing
Supports .srt, .vtt, .sbv, and .ass.
Converted Subtitle Preview
Why Frame Rate Conversion Matters for Video Editors
In professional video workflows, film is authored at 23.976 or 24.000 frames per second, while television broadcast standards vary regionally. European television (PAL) operates at 25.000 fps, while American and Japanese television (NTSC) operates at 29.970 fps.
When a video file is telecined or sped up from 23.976 fps to 25.000 fps, the video runs approximately 4.1% faster. If the accompanying subtitle file is not mathematically converted to match the new speed, the dialogue begins in sync at minute 0 but becomes visibly delayed as the movie progresses.
The Mathematical Conversion Formula
SubPreflight recalculates every individual timecode token using the exact frame rate ratio:
For a 23.976 fps to 25.000 fps conversion, the ratio is 23.976 / 25.000 = 0.95904. A cue originally occurring at 1 hour (3,600,000 ms) is shifted to 3,452,544 ms (57 minutes and 32 seconds), perfectly matching the European PAL broadcast run time.