Audio Normalizer (Peak and LUFS Loudness)

Make audio files play at a consistent level. Peak normalization raises or lowers a file so its loudest sample hits a target such as −1 dBFS. Loudness normalization measures how loud the file actually sounds, in LUFS, the way Spotify, YouTube, Apple Music and broadcasters do, and brings it to a target such as −14 or −16 LUFS while keeping the peaks under a true-peak ceiling. Several files can be brought to the same loudness at once, in your browser.

How to use this tool

1. Choose one or more audio files.
2. Pick "Loudness" and a target (−14 LUFS for streaming, −16 for podcasts, −23 for broadcast), or "Peak level" and a dBFS target.
3. Keep the true-peak ceiling at −1 dBTP unless a platform asks for something else.
4. Choose the format and press Calculate; the results show the loudness and peaks before and after.

Formula

Loudness (LUFS) = −0.691 + 10 × log10(mean square of the K-weighted signal) · gain = target − measured

The meter follows ITU-R BS.1770-4: the audio is K-weighted (a high shelf around 1.7 kHz and a high-pass near 38 Hz), measured in 400 ms blocks every 100 ms, blocks below −70 LUFS are ignored, then blocks more than 10 LU below the average; the rest give the integrated loudness. Loudness range follows EBU Tech 3342. The true peak is found with 4× oversampling, which can read up to about half a decibel low for the very highest frequencies, like other 4× meters. When the gain would push the true peak over the ceiling, a 5 ms look-ahead limiter lowers only those peaks, and the true peak is checked again. Lossy outputs are decoded again to make sure they do not clip.

Example

A podcast measured at −21.4 LUFS with a true peak of −4.8 dBTP, normalized to −16 LUFS, gets +5.4 dB: its peaks would reach +0.6 dBTP, so the limiter trims them to −1 dBTP and the episode ends up at about −16.1 LUFS. Peak normalization of a file peaking at −8.7 dBFS to −1 dBFS simply adds +7.7 dB.