Loudness and true peak: a practical guide for mixing and mastering
Two numbers decide whether a master translates: how loud it sounds and how high it actually peaks. Get loudness wrong and your track is turned down (or up) on streaming until it sits like everything else. Get true peak wrong and it clips after encoding — on the exact files your listeners hear. This guide is the whole picture; each section links to a deeper dive.
Loudness: measured in LUFS
Loudness isn't peak level and it isn't RMS — it's perceived loudness, measured in LUFS (Loudness Units relative to Full Scale) under ITU-R BS.1770, using K-weighting and gating so the number tracks how loud a track actually sounds. If that's new, start with What is LUFS?.
The reason it matters for release: streaming platforms normalize playback by integrated LUFS. Most music services reference around −14 LUFS (Apple Music sits a little lower). Master louder than that and you don't get louder — you get turned down, minus the dynamics you spent getting there. So the move is to master for the song and use LUFS as a check, not a target to beat. The platform-by-platform numbers are in LUFS targets for Spotify, Apple Music & YouTube.
True peak: measured in dBTP
Your peak meter shows sample peak — the tallest stored sample. But playback reconstructs a continuous waveform between the samples, and that waveform can rise higher than any sample. That overshoot is an inter-sample (true) peak, and it's why a master reading −0.1 dBFS can still clip in a converter or after MP3/AAC encoding. The full explanation is in True peak vs sample peak.
The fix is to measure and limit true peak (in dBTP), leaving headroom below 0. The common default is −1 dBTP, for reasons and step-by-step settings covered in How to set a true-peak ceiling.
Putting it together
On the master bus, loudness and true peak are two different jobs handled by two different controls:
- Loudness — drive level (input gain into your limiter) until the integrated LUFS reads where you want it for the material. Check it; don't chase a number past the point the mix suffers.
- True peak — set a true-peak ceiling at −1 dBTP (−2 dBTP for very dense masters or podcast specs) so nothing clips downstream.
That's the whole checklist: master for the music, verify loudness in LUFS, and hold true peak to −1 dBTP. Loudness decides how you sit next to other tracks; true peak decides whether you survive the encoder.
Takeaways
- Loudness = perceived level in LUFS (ITU-R BS.1770); streaming references ≈ −14 LUFS, so master for the song and use LUFS as a check.
- True peak = the reconstructed waveform's real maximum in dBTP; a master under 0 dBFS sample peak can still clip — hold true peak to −1 dBTP.
- They're separate controls: input/drive sets loudness, the ceiling protects peaks.