The units side by side
| Unit | What it measures | Reference | Where you meet it |
|---|---|---|---|
| LUFS (= LKFS) | perceived loudness: K-weighted, gated, averaged over time | digital full scale | loudness targets: Spotify -14 LUFS, EBU R 128 -23 LUFS |
| LU | a difference between two loudness readings | relative | offsets, Loudness Range (LRA) |
| dBFS | sample level | 0 dBFS = the largest value a fixed-point file can hold | sample peak meters, headroom |
| dBTP | true peak: the level between samples, found by oversampling | digital full scale | true-peak ceilings: -1 dBTP |
| dB SPL | acoustic sound pressure in the room | 20 µPa | how loud your speakers play |
EBU R 128 introduced LU and LUFS and states that LUFS is equivalent to LKFS, the name used in ITU-R BS.1770.
How a LUFS reading is made
K-weighting. Before anything is measured, the signal passes a two-stage filter: a shelving stage that models the acoustic effect of the head and a high-pass stage. Low bass counts for less than the midrange, roughly as hearing does.
Blocks and gating. For integrated loudness, BS.1770 measures 400 ms blocks with 75% overlap and ignores blocks below an absolute gate of -70 LKFS, then those more than 10 LU below the result. Silence and very quiet passages therefore do not drag the reading down.
Three time scales. EBU Tech 3341 defines Momentary loudness (a 0.4 s window), Short-term loudness (3 s) and Integrated loudness (the whole programme, gated). A meter showing -9 Momentary and -14 Integrated on the same track is not contradicting itself.
Why 1 LU is 1 dB, but -14 LUFS is not -14 dB
Both scales are logarithmic with the same step. BS.1770 notes that raising a signal by 1 dB raises the loudness reading by 1 LKFS, and EBU Tech 3341 states that 1 LU is equivalent to 1 dB. Turn a master up 2 dB and it measures 2 LU louder.
But a loudness reading and a peak reading are different quantities. A track measuring -14 LUFS integrated can have peaks close to -1 dBTP. The gap between the two, true peak minus integrated loudness, is the peak-to-loudness ratio: 13 dB in this example. A heavily limited master at -8 LUFS with the same -1 dBTP ceiling has only 7 dB.
dBFS vs dBTP: the peak you do not see
A sample-peak meter reads the samples in the file. The waveform a converter reconstructs can pass between those samples and rise higher. ITU-R BS.1770 measures this true peak by oversampling, 4× at 48 kHz (to 192 kHz), and reports it in dBTP.
This is why Spotify recommends keeping true peak below -1 dBTP so lossy transcoding does not add distortion, and below -2 dBTP for masters louder than -14 LUFS. Apple asks for at least 1 dB of headroom for the same reason. See what true peak is.
Common mistakes
Comparing different time scales. A Momentary reading on a loud chorus is not the track's integrated loudness.
Reading RMS as LUFS. RMS is unweighted and ungated; the two can differ by several dB on the same file. See RMS vs LUFS.
Treating -14 LUFS as a ceiling or a goal. It is Spotify's playback reference. A quieter master is turned up only as far as its peak headroom allows, a louder one is turned down.
Measuring it in Quantara
The studio measures the integrated loudness of your master to ITU-R BS.1770 and reports its true peak alongside, so you can read both numbers on the same track; while you play, the meter shows momentary loudness. A free account includes one free export per account (MP3 320, with a watermark), no card required. Open the studio.
Frequently asked questions
A difference of 1 LU equals 1 dB (EBU Tech 3341). LUFS itself is an absolute loudness reading, so a track at -14 LUFS does not have a level of -14 dB on a peak meter.
No. It is Spotify's normalization reference, not a limit. A master louder than -14 LUFS is turned down on Spotify's default setting, and Spotify recommends keeping its true peak below -2 dBTP.
Yes. EBU R 128 states that LUFS is equivalent to LKFS, the unit used in ITU-R BS.1770.
Peak and loudness measure different things. Peaks are instantaneous; integrated LUFS is a weighted, gated average over the whole track. The difference between them is the peak-to-loudness ratio.
Sources
ITU-R BS.1770-5: Algorithms to measure audio programme loudness and true-peak audio level (2023) — International Telecommunication Union
EBU R 128 v5.0: Loudness normalisation and permitted maximum level of audio signals (2023) — European Broadcasting Union
EBU Tech 3341 v4: Loudness Metering, 'EBU Mode' metering to supplement EBU R 128 (2023) — European Broadcasting Union
Loudness normalization on Spotify — Spotify for Artists