Measuring loudness: LUFS

LUFS (loudness units relative to full scale) measures loudness the way we hear it, following the ITU-R BS.1770 standard. Before measuring, the signal is filtered to match the ear: very low bass counts for less, and the upper mids and highs count for a little more. That is why a mix heavy in sub bass can read surprisingly quiet, and why a little more presence reads louder.

Integrated loudness

The loudness of the whole track: the number streaming services normalise to. Silence and very quiet passages are left out (anything below −70 LUFS, then anything more than 10 LU below the average), so adding silence or a quiet intro doesn't change it.

Short-term loudness

Loudness over a sliding 3-second window. It shows how loud each section is. The loudest short-term reading is how hard your chorus or drop hits.

Momentary loudness

The same over 0.4 seconds. It moves with individual hits and words.

Loudness range (LRA)

How much the short-term loudness varies across the song, in LU, ignoring the quietest 10% and loudest 5%. Roughly, under 5 LU is very consistent and 6 to 10 is typical of songs with breakdowns.