LUFS stands for Loudness Units relative to Full Scale. It comes from the ITU-R BS.1770 standard, which EBU R128 builds on. A LUFS meter filters the audio to match how ears hear it, then averages the level over a stretch of time. One LU is one dB of change, so a master at −10 LUFS is 4 dB louder than one at −14 LUFS.
That number matters because streaming services play music by it. Spotify plays tracks at −14 LUFS integrated by default, so a master measured at −10 LUFS gets turned down 4 dB. A peak meter can't tell you that. A LUFS meter can.
What a LUFS meter measures
A LUFS meter does three things a plain level meter doesn't.
- It applies K-weighting before measuring. K-weighting is a high-shelf boost and a low cut that approximate how ears hear. Deep bass counts for less, and the upper range counts for a little more.
- It averages the weighted level over a time window: 400 ms, 3 seconds or the whole song, depending on the reading.
- For the whole-song reading, it gates out silence and very quiet passages so they don't pull the number down.
"Relative to full scale" means the reference is the top of the digital scale. Real music reads as negative numbers. A quiet acoustic master might read −18 LUFS, a dense, heavily limited one −8 LUFS. Higher (closer to zero) means louder.
LUFS vs dB
A decibel is a ratio. It needs a reference to mean anything, and the letters after "dB" name that reference. dBFS on a peak meter tells you the highest sample in the file. It says nothing about how loud the song sounds.
Take two masters that both peak at −1 dBFS. One is a sparse piano piece, the other a compressed rock mix. The peak meter shows the same number for both. A LUFS meter could show the piano at −18 LUFS and the rock mix at −9 LUFS, a 9 LU gap that matches what you hear.
LUFS and dB still line up for changes. Turn a track down 3 dB with a fader and its LUFS reading drops by 3 LU. That is why a streaming service can take your integrated LUFS, compare it with its target and work out the exact gain change.
Peak level still matters for clipping. The modern way to read it is true peak in dBTP, which catches peaks between samples. The true peak guide covers dBTP vs dBFS and why −1 dBTP is the usual ceiling.
LUFS vs RMS
An RMS meter averages the signal's level, but it treats every frequency the same and has no gate. A loud sub-bass line pushes an RMS reading up as much as a vocal at the same level, even though ears hear the vocal as louder. A long fade or a silent intro drags an RMS average down.
LUFS fixes both problems. K-weighting cuts the low end's share of the reading, and the gate ignores silence. So two tracks at the same integrated LUFS sound close in loudness, which two tracks at the same RMS often don't. That is why the streaming services and broadcast standards use LUFS.
Integrated, short-term and momentary
A LUFS meter usually shows three readings. They measure the same thing over different windows. Meters often label them I, S and M, which is what people mean by "LUFS-I" or "LUFS M and LUFS S".
| Reading | Label | Window | Use it to |
|---|---|---|---|
| Momentary | M | 400 ms | See the loudness of a single hit, word or drop |
| Short-term | S | 3 seconds | Compare a verse with a chorus, or follow loudness through the song |
| Integrated | I | The whole song, gated | Get the one number streaming services use |
How gating works
The integrated reading uses two gates. An absolute gate drops anything below −70 LUFS, which removes silence. A relative gate then drops anything more than 10 LU below the ungated level, which removes very quiet passages.
Here is what that does in practice. Add 20 seconds of silence to the end of a song and an RMS average falls. The integrated LUFS stays where it was, because the absolute gate throws the silence away.
Which reading matters
For a delivery target, use integrated. When a service says −14 LUFS, it means integrated loudness of the whole track. Short-term and momentary help while you work. A chorus might sit at −8 LUFS short-term in a song that measures −11 LUFS integrated, and that gap is part of how the song moves.
LU and loudness range
LU is the relative unit that goes with LUFS. LUFS is an absolute level, LU is a difference. "This master is 2 LU louder than the reference" means the same as "2 dB louder" on a LUFS meter.
Loudness range, or LRA, is measured in LU. It describes how much the loudness varies across the song. A track with quiet verses and a loud chorus has a wider LRA. A master limited hard from start to finish has a narrow one. LRA has no single right value. Use it to see how much of the song's movement survived the limiter.
How to measure LUFS
Measure the exported file, from start to end, and read integrated LUFS and true peak together. A reading taken from a loop of the chorus will be louder than the whole song. A reading taken from a speaker through a microphone measures the room as well as the file.
ABSeq does this for every file you load. Each track shows its integrated LUFS, measured to ITU-R BS.1770 and EBU R128, and its true peak in dBTP. With Pro, the LUFS graph plots short-term loudness across the whole song against a −14 LUFS line, and its readout shows S, M and I. The guide to measuring LUFS on iPhone walks through it step by step.
Once you have the number, the next question is what it should be. The LUFS targets for each streaming service list what Spotify, Apple Music, YouTube and the others play at. A master louder than the target isn't rewarded. The service turns it down, and it plays at the same level as a quieter master, with less dynamic range left.
LUFS also matters when you compare two versions. Ears hear a louder version as fuller and brighter, and a gap of about 1 dB is enough to bias the choice. Match the versions by integrated LUFS before you judge them. The level matching guide explains how.
Questions
What does LUFS mean?
LUFS means Loudness Units relative to Full Scale. It is a loudness unit defined in ITU-R BS.1770 and used by EBU R128. The meter applies K-weighting, a high-shelf boost and a low cut that approximate how ears hear, then averages the level over time. One LU equals one dB of change.
Is LUFS the same as dB?
No. dB on a peak meter shows the highest sample, which says little about how loud a song sounds. LUFS measures perceived loudness over time. Changes do line up, though. Turn a track down 3 dB and its LUFS reading drops 3 LU.
What is LUFS-I?
LUFS-I is integrated loudness, the average over the whole song with gating. The absolute gate drops anything below −70 LUFS and the relative gate drops anything more than 10 LU below the ungated level, so silence and quiet gaps don't pull the number down. Streaming targets such as Spotify's −14 LUFS refer to integrated loudness.
What is the difference between LUFS M and LUFS S?
LUFS M is momentary loudness, measured over a 400 ms window, so it follows single hits and words. LUFS S is short-term loudness over 3 seconds, which shows how a verse compares with a chorus. Neither is a delivery target. Use integrated loudness for that.
Integrated LUFS vs short-term: which should I watch?
Watch short-term while you mix to see how loudness moves through the song, and check integrated on the final bounce. A chorus can read −8 LUFS short-term in a song that measures −11 LUFS integrated. Only the integrated number decides how much a streaming service turns the track down.