True Peak, RMS, and LUFS: Three Loudness Metrics You Should Actually Understand

If you only look at one number during mastering, you're probably missing something. LUFS tells you whether your track is streaming-ready. True Peak protects you from distortion during conversion. RMS is an older tool that rarely matters today but still shows up here and there. Once you know what each metric is actually measuring, mastering stops feeling like guesswork.

True Peak: The Level Hiding Between Your Samples

True Peak (TP) doesn't just measure the digital sample values — it captures the reconstructed level between samples too, known as inter-sample peaks. That matters because during digital-to-analog conversion, the waveform gets interpolated between samples, and that interpolation can produce peaks higher than the loudest digital sample you actually recorded.

In practice: a track peaking at −0.3 dBFS digitally can still hit real peak levels above 0 dBFS after D/A conversion — and on some playback systems, that causes audible distortion.

Rule of thumb: streaming platforms like Spotify, Apple Music, and YouTube expect a max of −1 dBTP; club systems are usually fine up to −0.1 dBTP.

Beatzucker displays your track's True Peak value both before and after mastering, so you always know where you stand.

RMS: Yesterday's Loudness Standard

RMS (Root Mean Square) calculates the quadratic mean of a signal and was the go-to loudness reference before LUFS took over. The catch: RMS measures raw signal energy, not how loud a human actually perceives that signal — psychoacoustic weighting plays no role in the calculation.

Because of that, RMS barely functions as a primary metric in modern mastering anymore. You'll mostly still encounter it in older DAW manuals or legacy workflows. If you're mastering for streaming, you can safely ignore RMS and lean entirely on LUFS instead.

LUFS: Today's Loudness Benchmark

LUFS (Loudness Units relative to Full Scale) measures loudness the way humans actually perceive it, following the ITU-R BS.1770 and EBU R128 standards. It applies frequency weighting based on human hearing (K-weighting) and represents the average loudness across an entire track.

There are three variants worth knowing:

Integrated LUFS: the average across the whole track — this is the number streaming services use for loudness normalization.

Short-Term LUFS: a rolling average over the last 3 seconds, useful for spotting dynamic swings within a track.

Momentary LUFS: a rolling average over the last 0.4 seconds, giving you near real-time visibility into short-term loudness spikes.

The Short Version: Which Metric, When?

A quick cheat sheet for everyday use:

• True Peak: check it right before export — max. −1 dBTP for streaming releases.
• Integrated LUFS: verify after mastering — the target depends on the platform (−14 for Spotify, −16 for Apple).
• Short-Term LUFS: keep an eye on it while mixing to track dynamics.
• RMS: only relevant for legacy systems or older broadcast specs.