Audio Loudness Normalizer

LUFS (Loudness Units relative to Full Scale) is the standard measurement for perceived audio loudness. Unlike peak or RMS meters, LUFS accounts for how human ears perceive sound across different frequencies (using K-weighting). Streaming platforms use LUFS to ensure consistent playback volume across all tracks, preventing jarring volume jumps between songs.

Spotify normalizes audio to approximately -14 LUFS Integrated. While Spotify's normalization can be turned off, mastering to -14 LUFS with a True Peak of -1 dBTP is widely recommended. Note that Spotify applies its own loudness normalization, so tracks mastered louder will simply be turned down.

YouTube normalizes to around -14 LUFS (similar to Spotify). Apple Music uses -16 LUFS as their reference level for Apple's Sound Check feature. Amazon Music also targets -14 LUFS. For maximum compatibility across platforms, mastering between -14 and -16 LUFS is a safe bet.

True Peak (dBTP) measures the absolute maximum signal level, including inter-sample peaks that occur during digital-to-analog conversion. Limiting True Peak to -1 dBTP (or -2 dBTP for broadcast) prevents clipping distortion when audio is converted to analog or compressed to lossy formats like MP3/AAC. Standard peak meters miss these inter-sample peaks.

Integrated LUFS measures the average loudness of the entire audio file (using gated measurement per EBU R128). Short-term LUFS uses a 3-second sliding window, showing how loudness changes throughout the track. Momentary LUFS uses a 400ms window for near-instantaneous readings. Integrated is most important for mastering.

Loudness Range (LRA) measures the variation in loudness throughout a track, expressed in LU (Loudness Units). A higher LRA indicates more dynamic range (e.g., classical music may have LRA > 10 LU). A lower LRA suggests a more compressed, consistently loud track. Typical pop music has an LRA of 4–8 LU. LRA helps you understand your audio's dynamic character.

This tool implements the EBU R128 / ITU-R BS.1770-4 algorithm using K-weighting filters, gated measurement, and True Peak oversampling detection — all running in your browser via Web Audio API. While it provides very close approximations (typically within ±0.5 LU of professional tools like Youlean Loudness Meter or iZotope Insight), for critical mastering work we recommend cross-referencing with dedicated desktop metering plugins.

For podcasts, the recommended target is -16 LUFS for stereo and -19 LUFS for mono, with a True Peak limit of -2 dBTP. This follows the AES recommended practices for podcast loudness. Apple Podcasts and Spotify both recommend -16 LUFS. Use the "Podcast -16" preset in this tool for quick setup.