What is LUFS?

LUFS (Loudness Units Full Scale) is a standardized measurement of how loud a piece of audio sounds over time, as defined by ITU-R BS.1770 and adopted by the EBU's R128 recommendation. It's the measurement behind the loudness normalization used by every major streaming platform and broadcaster -- Spotify, Apple Music, YouTube, Netflix, and EBU broadcast delivery all specify their targets in LUFS.

What makes it different from a plain level reading

Two things separate LUFS from an ordinary peak or RMS meter:

• K-weighting. The signal is filtered to approximate how the human ear perceives loudness at different frequencies before it's measured -- a boost to the low end registers differently than a boost to the highs, because that's how people actually hear it.
• Gating. Silence and very quiet passages are excluded from the measurement window, so a track with a long quiet intro or outro isn't dragged down by sections nobody would call "the loudness of the track."

The result is integrated LUFS: a single number describing a whole track's perceived loudness, referenced directly to full scale. Because of that reference point, a LUFS value also tells you exactly how much headroom is left below clipping -- a track at -8 LUFS is, roughly speaking, sitting 8 dB below full scale.

Why it replaced simpler measurements

Before loudness normalization, a track's perceived volume on playback was mostly a function of how hard it had been limited in mastering -- the "loudness war" of the 2000s. A peak meter alone can't distinguish between a dynamic mix that occasionally hits 0 dBFS and a heavily limited mix that sits at 0 dBFS almost constantly, even though the second one sounds dramatically louder. LUFS measures the thing listeners actually perceive, so a platform can turn every track down (or up) to the same target and let dynamics -- not brute-force limiting -- do the work of standing out.

Where you'll see it

Every release measured on lufs.to reports its integrated LUFS (the whole-track figure), alongside true peak, loudness range (LRA), and short-term max -- see Methodology for exactly how each is computed. To convert a LUFS reading into other units, or check it against a specific platform's target, see the LUFS & dB converter.

See also: LUFS vs RMS -- how LUFS compares to the older, simpler RMS measurement it largely replaced.