LUFS stands for Loudness Units relative to Full Scale. It measures how loud audio sounds, weighting frequencies the way human hearing does, rather than how high its peaks go. The measurement is defined in the ITU-R BS.1770 standard. One loudness unit (LU) is the same size as one decibel.
Why it matters
Two files can peak at the same level and sound very different in loudness. Platforms normalize everything to a target loudness, so a file mastered far above the target gets turned down, and one far below it sounds weak next to everything else.
The number that usually matters is integrated loudness: the average over the whole file.
Common targets
| Where it’s going | Target |
|---|---|
| Broadcast (EBU R128) | −23 LUFS |
| Podcasts (Apple’s recommendation) | −16 LUFS |
| Music streaming (Spotify’s normalization) | −14 LUFS |
Audiobooks for ACX/Audible use a different measure (RMS level between −23 and −18 dB, with peaks no higher than −3 dB).
Setting it in practice
Loudness tools measure the file and adjust its gain to hit a target. In Gleam Audio, the Enhance tool does this with presets for music streaming, podcasts, audiobooks and broadcast.