For decades, the game was simple: push it as loud as possible. Stack limiters, squeeze every last dB of headroom, make your master clip the meters and hope radio stations would just deal with it. That was the loudness war — and it made music sound worse.
Streaming platforms ended it by flipping the script. Spotify, Apple Music, and YouTube all measure how loud your track is over time and turn it down if it exceeds their target. Suddenly, smashing a master louder than -8 LUFS got you nowhere — the platform just attenuated it back, and the distortion artifacts stayed. Engineers who understood LUFS started winning. The ones still mixing to the red started sounding worse.
So: what is LUFS, actually, and what do you need to know to use it?
What LUFS Actually Measures
LUFS stands for Loudness Units relative to Full Scale. It is numerically identical to LKFS (Loudness, K-weighted, relative to Full Scale) from the ITU-R BS.1770 standard — the two terms describe the same measurement, just from different standards bodies. You will see both in the wild.
LUFS is not a peak meter. It is a perceptual loudness measurement that works the way your ears work. Two elements make it accurate:
- K-weighting filter: Human hearing is more sensitive in the midrange (roughly 1-4 kHz) than at low or very high frequencies. A K-weighted measurement applies a filter that emphasizes those frequencies — so a bass-heavy mix and a vocal-heavy mix with the same peak levels will measure differently, matching what you actually perceive as louder.
- Gating: Long sections of silence would drag down the integrated loudness of any track. LUFS metering ignores audio that falls below an absolute threshold (-70 LUFS) and a relative threshold (10 LU below the running average). This means the quiet fade-out at the end of your track is not pulling down the number that represents how the record actually sounds.
Three measurement windows give you three different views:
- Momentary LUFS: 400ms window. Tells you what is loud right now. Useful for checking individual hits, leads, and transients in real time.
- Short-term LUFS: 3-second window. Smoothed enough to track sections — chorus vs. verse, build vs. drop. Good for spotting imbalances between song sections.
- Integrated LUFS: The full program measurement from start to finish, with gating applied. This is the number streaming platforms compare against their normalization targets. When someone says "master to -14 LUFS," they mean integrated.
LUFS vs. dBFS vs. RMS — What's the Difference?
These three measurements are answering different questions:
| Measurement | What it measures | Useful for |
|---|---|---|
| dBFS | Peak sample level — the highest individual sample value in the file | Checking headroom, preventing clipping before export |
| RMS | Root mean square — average power over a window, no frequency weighting | Rough loudness estimate; used in older workflows before LUFS standards |
| LUFS | Perceptual loudness with K-weighting and gating, referenced to full scale | Matching streaming platform targets; comparing perceived loudness across tracks |
RMS gave engineers a better measure of loudness than peak metering alone, but it ignores how humans actually hear different frequencies. LUFS supersedes RMS for any work destined for streaming. dBFS still matters for headroom — you will need it when setting a true peak ceiling (see below).
Streaming Platform Loudness Targets
Every major platform measures your track's integrated loudness and applies normalization. If your master comes in louder than the target, the platform turns it down. If it comes in quieter, most platforms leave it alone rather than turn it up — which means a master at -18 LUFS will simply play back at -18 LUFS and sound quieter relative to everything else in the queue.
| Platform | Integrated Target | True Peak Max | Notes |
|---|---|---|---|
| Spotify | -14 LUFS | -1 dBTP | Normalization can be disabled by listeners; default on |
| Apple Music | -16 LUFS | -1 dBTP | Sound Check; more conservative target means more dynamic masters benefit |
| YouTube | -14 LUFS | -1 dBTP | Always-on normalization; users cannot disable it |
| Tidal | -14 LUFS | -1 dBTP | Only attenuates loud masters; does not boost quiet ones |
| Amazon Music | -13 LUFS | -2 dBTP | Slightly louder reference; stricter true peak ceiling |
| SoundCloud | -14 LUFS | -1 dBTP | Normalization on by default since 2019 |
For broadcast (TV, radio), the EBU R128 standard specifies -23 LUFS integrated — significantly more headroom than streaming. If you are delivering to a broadcaster, that is a separate target entirely.
The practical takeaway: mastering to -14 LUFS integrated covers Spotify, YouTube, Tidal, and SoundCloud exactly, and means Apple Music and Amazon Music apply minimal normalization. A true peak ceiling of -1 dBTP is safe for all platforms except Amazon, which wants -2 dBTP — so -2 dBTP is the conservative choice if you want one master to rule them all.
True Peak vs. Sample Peak
Your DAW's peak meter shows you the highest sample value in your file. That is the sample peak. It is useful for preventing clipping inside the DAW, but it is not the whole picture.
When a digital audio file is played back, the DAW or device performs digital-to-analog conversion — it reconstructs a continuous waveform from the discrete sample values. That reconstruction process uses interpolation, and the resulting analog waveform does not always peak exactly where your sample meter showed. Sometimes it peaks higher. Those higher points are called inter-sample peaks, and the maximum value of the fully reconstructed waveform is the true peak.
This matters for streaming because lossy encoding (AAC, Ogg Vorbis, MP3) makes it worse. Encoding discards and reconstructs audio information, and the reconstructed file can measure significantly higher in true peak than the original. A file at +0.0 dBFS sample peak can easily measure +1.0 dBTP or higher after being encoded to AAC.
True peak metering works by oversampling the audio (typically 4x or higher) to estimate the reconstructed waveform and measure what it will actually do. Setting a true peak ceiling of -1 dBTP gives that headroom buffer so codec artifacts stay below clipping.
LRA: Loudness Range
Integrated LUFS tells you how loud the whole track is. LRA — Loudness Range — tells you how dynamic it is.
LRA is measured in LU (Loudness Units) and describes the statistical spread between the quietest and loudest sections of a program, excluding the very top and bottom tails of the distribution. A track with an LRA of 3 LU is highly compressed — the verse and the chorus hit almost the same perceived loudness. A track with an LRA of 14 LU has wide dynamic variation, like a classical recording or a track with very spare production in the verses.
LRA does not have a single correct value. A heavily produced club track might target 4-6 LU. A folk record might sit at 10-12 LU. What LRA reveals is whether your dynamics decisions in the mix are landing the way you intended. If a mix that should feel dynamic is showing an LRA of 3 LU, something is over-compressed. If a track that should feel dense and energetic is showing 14 LU, the master is not controlled enough.
For a complete guide to using your phone as a reference monitor while mixing, see Phone as Studio Monitor — The Engineer's Guide.
How to Check LUFS in Real Time While You Mix
The traditional workflow puts loudness checking at the end: finish the mix, export, run it through a loudness meter, go back and adjust, export again. Loudness becomes an afterthought applied to a finished mix rather than a dimension you shape as you work.
There is a better way to think about it. Loudness is about how a track feels at listening volume, in a real listening environment — not how it looks in a meter in your studio. The most useful moment to check it is while you are actually listening: walking the room, standing at the back, listening on your phone the way your audience will.
That is exactly what Auxfeed is built for. The plugin streams audio from your DAW directly to your phone in real time, with zero export step. The free tier includes Momentary LUFS metering on your phone while you walk around and listen — you can see what is hitting loud right now, in the context of how the track actually sounds in your ears at that moment.
Auxfeed Pro ($9.99/month or $79/year) adds Integrated LUFS, Short-term LUFS, True Peak, and LRA to the mobile meters, plus per-platform loudness targets for Spotify, Apple Music, and YouTube. Instead of finishing a mix and discovering it measures -8 LUFS integrated, you know while you are still working.
Auxfeed is free at auxfeed.com. Momentary LUFS metering is included free — upgrade to Pro for integrated LUFS, true peak, LRA, and per-platform loudness targets.