What Is LUFS? Loudness Explained with Measured Audio

A peak meter can show two recordings reaching the same maximum while their sustained levels differ. LUFS helps describe that difference. It is a standardized measurement, not a headphone-volume percentage or a personal hearing test.

What does LUFS mean?

LUFS means Loudness Units relative to Full Scale. LKFS is the closely related notation used in some delivery specifications; the numerical readings are treated equivalently for program-loudness reporting. ITU-R BS.1770-5 is the current in-force reference for program-loudness and true-peak algorithms.

The calculation weights frequency and channels before combining energy. It does not fully describe every listener’s experience: device response, room noise, hearing, duration and the recording’s internal dynamics still matter.

Integrated, short-term and momentary LUFS

The EBU metering specification distinguishes momentary readings over 400 milliseconds, short-term readings over three seconds, and integrated readings across the measured program with gating. Gating excludes sufficiently quiet material according to the meter’s rules; integrated LUFS is not simply the average of every displayed momentary number.

Use integrated loudness for a completed episode or song. Examine shorter readings when one sentence disappears or an effect dominates. Two episodes with the same integrated value can still have very different quiet and loud passages.

Hear the difference: equal peaks, different loudness

We generated two original 10-second, 480 Hz signals. Both are mono, 48 kHz, 16-bit PCM WAV files with the same maximum sample amplitude. One sustains its level; the other repeatedly drops to one-quarter amplitude. Start playback at a low, comfortable device volume and keep it unchanged between samples.

Steady tone — 10 seconds

Download steady tone WAV (0.96 MB)

Pulsed tone — 10 seconds

Download pulsed tone WAV (0.96 MB)

Measurement	Steady	Pulsed
Sample peak, dBFS	−18.062	−18.062
Integrated LUFS	−21.7	−27.5
True peak, dBTP	−18.1	−18.1

The measured difference is 5.8 LU despite identical sample peaks. This does not imply a fixed percentage difference in perceived loudness. Mono playback mapping and output hardware affect what you hear.

Reproduce the measurements

We measured the complete files on September 19, 2026 using FFmpeg 9.0.1 and its ebur128 scanner, default gating, mono channel layout and true-peak estimation. The meter rounds its summary to one decimal place. Run this command on each downloaded file:

ffmpeg -hide_banner -nostats -i steady.wav -af ebur128=peak=true -f null -

Change steady.wav to pulsed.wav for the second sample. The filter measures the file; this command does not normalize or export it. Our generator source, measurements and SHA-256 checksums, steady log and pulsed log document the envelope and method.

This is a synthetic measurement example, not an extension or streaming-platform benchmark, and not an independently certified standards-conformance test.

How do LU, dBFS and dBTP differ?

LU describes a relative loudness difference. Sample-peak dBFS reports the largest stored sample. True-peak dBTP estimates reconstructed peaks that can occur between samples. A loudness target and a peak ceiling answer separate questions: average program level and remaining headroom.

Turning down a clipped recording reduces its level; it does not restore the waveform that was lost. Conversely, a recording can have substantial peak headroom and still be hard to follow because a voice is masked by music.

Is −14 LUFS the target for everything?

No. A measurement standard does not decide a platform’s playback policy. EBU R 128 uses a −23 LUFS broadcast reference; that is not a universal instruction for podcasts or web video.

Spotify’s documentation lists Normal at −14 LUFS, Loud at −11 and Quiet at −19, with headroom constraining some upward adjustments. Its web player does not use normalization. Our Spotify volume guide explains the practical distinction.

YouTube documents Stable volume for reducing differences within eligible videos, rather than a universal delivery target in that help page. See YouTube volume consistency for the available controls.

How should I measure a real episode?

Measure the entire edited program, then inspect quiet speech and loud transitions. Record the meter version, channel layout, file version, gating and true peak. Apply the destination’s current specification and recheck the final encoded deliverable. The podcast release checklist connects these measurements to listening checks.

Does Hearably normalize a tab to a LUFS target?

Hearably changes supported browser-tab audio after capture begins. Gain, EQ and compression can change listening levels, but it does not currently measure a live tab to a guaranteed integrated-LUFS target. Its limiter benchmark concerns digital sample peaks, not loudness normalization. More gain can expose source noise or overload playback hardware; it cannot reconstruct missing detail or establish a safe acoustic level.