What is LUFS? Loudness units, explained.
LUFS is the unit streaming services and broadcasters use to measure how loud audio sounds, not how high its peaks go. Here is what it measures, how it is calculated, and which LUFS numbers matter for your master.
BY OKAN ÇAM · UPDATED
THE SHORT VERSION
- LUFS stands for Loudness Units relative to Full Scale. It measures perceived loudness, not peak level.
- It is defined by ITU-R BS.1770: the signal is filtered to match how we hear (K-weighting), then its power is averaged over time.
- Integrated LUFS covers the whole file, short-term a 3-second window and momentary a 400 ms window.
- A change of 1 LU is a change of 1 dB. LKFS is the same unit under its US broadcast name.
- Streaming services play every track at a set loudness: −14 LUFS on Spotify and YouTube, −16 LUFS on Apple Music.
- Normal audio always reads negative. −8 LUFS is louder than −14 LUFS.
What does LUFS mean?
LUFS stands for Loudness Units relative to Full Scale. Full scale is the loudest level a digital file can hold, 0 dBFS, and a loudness unit is a step the same size as a decibel. So −14 LUFS reads as fourteen loudness units below full scale. Because it counts down from full scale, normal program material always reads negative: −8 LUFS is a loud master, −23 LUFS is European broadcast level.
What makes it different from a peak meter is what it listens to. A peak meter reports the single highest sample. LUFS averages the energy of the whole signal after filtering it the way our hearing works, so it follows how loud a song sounds. That is what a listener notices when one track follows another, and it is why streaming services and broadcasters use it.
How LUFS is measured
The method is ITU-R BS.1770, now at revision 5, and EBU R128 builds its broadcast rules on it. In short:
- 01K-weighting. A shelving filter lifts the highs by about 4 dB and a high-pass filter rolls off the deep lows, roughly the way the ear hears.
- 02Mean square. The power of the filtered signal is measured in 400 ms blocks that overlap by 75%.
- 03Channel sum. The channels are added up. Left and right count equally. In surround, the rear channels count a little more and the LFE channel is left out.
- 04Gating. Blocks below −70 LUFS are ignored, then blocks more than 10 LU below the average of what is left. Silence and quiet passages don't drag the number down.
- 05The result. The average of the blocks that pass the gates is the integrated loudness, in LUFS.
The gating is why a song with a quiet intro reads almost the same as the song without it, and why meters that follow BS.1770 agree on the same file. When two meters don't, it is almost always a setup difference, explained in why two loudness meters show different LUFS.
Integrated, short-term and momentary LUFS
- Integrated (I). The whole file, with gating. This is the number streaming services normalize to and the one delivery specs ask for.
- Short-term (S). A 3-second sliding window. Use it to compare sections: how loud the chorus sits against the verse.
- Momentary (M). A 400 ms window. It jumps with every hit, so it's for watching while you work, not for delivery numbers.
Two more numbers come from the same measurement: loudness range (LRA), from the spread of the short-term values, and PLR and PSR, which compare loudness with the true peak.
LUFS vs dBFS and RMS
dBFS is a level: how close the samples come to full scale. A peak meter in dBFS tells you whether a file clips, but not how loud it sounds. A short snare hit and a long synth pad can both peak at −1 dBFS and sound nothing alike.
RMS is closer. It averages power like LUFS does, but with no frequency weighting and no gating, so bass-heavy mixes read louder than they sound and silence pulls the number down. LUFS adds the weighting and the gating, which is why it replaced RMS for loudness targets.
The units line up: 1 LU is 1 dB. Turn a master up 2 dB and it reads 2 LU louder. LKFS, the name used in US broadcast documents such as ATSC A/85, is the same unit.
What LUFS should your master be?
There's no single right number. It depends on where the audio goes:
| Where it plays | Loudness | True peak |
|---|---|---|
| Spotify | −14 LUFS | −1 dBTP |
| Apple Music | −16 LUFS | −1 dBTP |
| YouTube | −14 LUFS | −1 dBTP |
| Apple Podcasts | −16 LUFS | −1 dBTP |
| EBU R128 broadcast | −23 LUFS | −1 dBTP |
| ATSC A/85 (US TV) | −24 LKFS | −2 dBTP |
For music, the streaming numbers are playback levels, not delivery rules. A louder master is turned down to them, and the loudness penalty calculator shows by how much. Broadcast is different: there the number is a requirement, and a programme that misses it can be rejected. Every platform is in the loudness targets table, and the Spotify, Apple Music and YouTube guides explain what each service does.
Measure the LUFS of your file
Drop your master into the online LUFS meter. It measures integrated, short-term and momentary LUFS, true peak, LRA, PSR and PLR in your browser, without uploading the file, and plays it at each streaming service's level so you can hear what normalization does. For a live reading while you mix, LOUDMETER: Menu Bar meters whatever your Mac is playing.
FAQ
What does LUFS stand for?
Loudness Units relative to Full Scale. It's the unit ITU-R BS.1770 defines for measuring perceived loudness, and the one EBU R128 and the streaming services use.
Is LUFS the same as dB?
It's a different measurement with the same step size: 1 LU equals 1 dB. dBFS measures sample level; LUFS measures loudness after K-weighting and gating.
Why is LUFS negative?
Because it counts down from full scale, the loudest level a digital file can hold. Normal audio sits below it, so the numbers are negative, and a number closer to zero is louder.
Is −14 LUFS loud?
It's a moderate level for music. Plenty of rap, EDM and metal is mastered around −9 to −6 LUFS. Spotify and YouTube play music at about −14 LUFS, so louder masters are turned down to it.
What is the difference between LUFS and LKFS?
None. LKFS is the name used in US broadcast documents such as ATSC A/85; LUFS is the European name. One LKFS equals one LUFS.
What LUFS should I master to for streaming?
About −14 LUFS avoids being turned down on Spotify and YouTube, but you don't have to hit it. Master for the sound you want, keep true peak below −1 dBTP, and check how it sounds at each platform's level.
Keep reading
Spotify LUFS
What −14 LUFS means, the Loud, Normal and Quiet settings, and how loud to master for Spotify.
Apple Music LUFS
Sound Check, the −16 LUFS level, AAC and lossless, and what they mean for your master.
YouTube LUFS
YouTube turns loud videos down and never turns quiet ones up. How to read content loudness.
SoundCloud LUFS
No normalization, so louder is louder. Why true peak matters more on SoundCloud than anywhere.
True Peak vs Sample Peak
Why a master that peaks at 0 dBFS can still clip, and why −1 dBTP is the number everyone quotes.
What Is LRA?
Loudness range, how it's calculated, typical values, and what it can't tell you.
PLR and PSR
Peak-to-loudness and peak-to-short-term ratio: how hard is your master limited?
Loudness Penalty
How much Spotify, Apple Music, YouTube and others turn your master down, with a calculator.
Youlean vs Loudmeter
An honest comparison: a DAW plug-in, and a browser analyzer with Mac and iPhone apps.
Why Meters Show Different LUFS
Same file, different numbers? The four setup mistakes behind almost every mismatch.
Loudness Targets for Every Platform
Streaming, podcast, broadcast and game targets in one table, with what each number means.
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