LUFS stands for Loudness Units relative to Full Scale, a unit for measuring the loudness of audio in a way that accounts for human hearing. Two files with the same peak value can feel different in loudness if their density or frequency balance differs, so LUFS is what you use when comparing the perceived loudness of songs and videos.
Momentary, Short-term, and Integrated
Momentary covers a very brief window, Short-term a few seconds, and Integrated the overall loudness from the start to the end of the measurement. For the delivery value of a whole song, or when comparing pieces of audio, you generally look at Integrated LUFS, written LUFS-I.
Frequency weighting and gating
LUFS measurement applies a weighting that reflects the ear’s differing sensitivity across frequencies. Integrated measurement also uses a gate that excludes sections below a certain threshold, so that long silences or extremely quiet passages do not pull the average down unnaturally.
How to measure correctly
Put a loudness meter on the final output, reset the value, and play from the very start of the song to the very end. The chorus alone, or the intro alone, will not give you the value for the whole piece. After making changes, reset again, measure the full song, and check Integrated and True Peak together.
Target values depend on the use
Streaming services and broadcast standards each have their own operating criteria, and there is no single correct number for all audio. Rather than forcing a specific figure, decide based on the destination’s latest specification, the dynamics of the music, and how it compares by ear with other material.
Matching several pieces of audio
LUFS-I makes it easier to even out level differences across songs that peak values alone struggle with. The batch loudness normalizer analyzes your files, adjusts them to a common LUFS-I target, and lets you check the True Peak ceiling as well.
