Measure loudness (LUFS)
Measure an audio file's (or a video's audio track's) integrated loudness in LUFS with ITU-R BS.1770-4 K-weighting and gating, plus an estimated true peak and loudness range, decoded through the same PCM path as audio-reverse. WAV decodes everywhere; other codecs need a browser.
Measure loudness (LUFS) scores a clip's integrated loudness under ITU-R BS.1770-4, applying K-weighting and gating, then reporting an estimated peak level and loudness range. At least 400 milliseconds of decoded audio is needed for one gating block. No file gets written back; the report is the whole result, and WAV decodes without a browser while other codecs need one.
Questions
What does the LUFS number mean?
It reflects loudness measured to the ITU-R BS.1770-4 recommendation, the same standard broadcast and streaming loudness targets are set against. A lower number, more negative, means quieter overall.
Does this change my file?
No. This tool is read only. It reports the measurement as text and produces no output file at all.
What does true peak mean here?
An estimate of the highest instantaneous level, including peaks that sit between samples, found by a fourfold interpolated oversample rather than a plain scan of the raw samples.
Why did it refuse my file?
Because BS.1770 gating needs at least 400 milliseconds of audio to measure a single block. A shorter file has nothing to gate and is refused with its length named.
What if my file is quiet throughout?
If every block falls below minus 70 LUFS, the absolute silence gate, the report says the integrated loudness sits below minus 70 LUFS rather than giving a false precise number.