The full form
LUFS — Loudness Units relative to Full Scale. You will also see LKFS (Loudness, K-weighted, relative to Full Scale) in broadcast documents. They are the same measurement with two names; the numbers are interchangeable.
The unit is defined in ITU-R BS.1770, an international standard, which is why a LUFS figure from one tool is comparable against a LUFS figure from another. That is the entire point of it, and it is what separates LUFS from the invented "loudness" and "energy" scores that different pieces of software each define differently.
Why the number is negative
The scale is measured relative to full scale. 0 LUFS is the ceiling — the loudest a digital file can theoretically be. Everything real sits underneath it, so every loudness reading you will ever see is negative.
That trips people up once and then never again:
- −9 LUFS is louder than −14 LUFS. Closer to zero is louder.
- A difference of 1 LU is a difference of 1 dB in level. Loudness Units and decibels move together, so turning a master down by 3 dB moves it 3 LU quieter.
- There is no bottom. Quiet material just keeps going negative.
LUFS, dBFS and RMS are three different questions
| Unit | What it answers |
|---|---|
| dBFS | How tall is the waveform? Sample values, nothing else. |
| RMS | What is the average energy? Better than peak, but deaf to frequency. |
| LUFS | How loud does this actually sound to a person? |
The difference that matters is frequency. LUFS applies a K-weighting — a filter curve written into the standard that follows human hearing, which is more sensitive in the upper mids than at the extremes. A bass-heavy master and a bright one can hit identical peaks and sound nothing alike in level; LUFS is the unit that notices.
The second difference is gating. The standard throws out silence and passages well below the average before it computes the figure, so a track with a long quiet intro is not scored as quieter than it plays. It is also why a naive average of a file and a proper integrated LUFS reading are different numbers.
Momentary, short-term, integrated
Three windows, one measurement:
| Window | Length | What it is for |
|---|---|---|
| Momentary | about 400 ms | Watching a mix move while you work. |
| Short-term | about 3 s | Section-level loudness — is the chorus lifting? |
| Integrated | the whole programme | One figure for a finished file. This is the one people mean. |
When somebody says "this master is −9", they mean integrated. It is the figure a platform compares against its target, and the figure worth checking before anything leaves your machine.
You may also meet LRA — loudness range — which describes how much the loudness varies across a programme rather than how loud it is.
What platforms do with it
Streaming services normalise playback: they measure the integrated loudness of what you uploaded and turn it up or down toward their own target so that one track does not blast the listener after another. Targets are commonly cited around −14 LUFS, and each platform publishes its own figure — check the platform's own documentation, because they have moved before and will again. Broadcast in Europe uses −23 LUFS under EBU R 128.
The practical consequence is the part worth internalising:
Mastering louder than the target does not make you louder. It makes you quieter and more compressed at the same playback level, because the platform turns the whole thing down and the dynamic range you traded away does not come back.
That is not an argument for mastering quiet. It is an argument for deciding the loudness of a record on musical grounds and knowing the number before you upload rather than after.
True peak is the other half
LUFS tells you how loud it sounds. True peak, measured in dBTP, tells you whether it will distort — it catches the peaks that appear between samples when a file is converted to analogue or re-encoded to a lossy format, which ordinary sample-peak metering cannot see.
The two are checked together, and both are defined in the same standard. More on true peak →
Measuring it
DropWave reports integrated LUFS and true peak in dBTP to ITU-R BS.1770-4 for any file you drop on it, alongside the key and tempo, and does it on your own machine — nothing is uploaded.
Reviewed 2026-08-18. Platform targets are published by the platforms themselves and change; the standard does not.