Loudness Meter (LUFS)
Check how loud a file really is against the standards used by streaming services and broadcasters.
MP3, WAV, M4A, FLAC, OGG, Opus, AIFF, WMA, AMR and the sound of most videos. Files stay on your device.
How it works
- Choose an audio file.
- Wait for the measurement to finish.
- Compare the numbers with the target for your platform.
What is measured
Integrated loudness is the average loudness of the whole file in LUFS, measured with the K-weighting and gating of ITU-R BS.1770-4. Loudness range (LRA) describes how much the loudness varies. The momentary value uses a 400 ms window and the short-term value a 3 second window; the page shows the highest of each and graphs the short-term loudness over time. True peak is the highest level of the reconstructed waveform, measured on a 4 times oversampled signal, so it can be higher than the highest sample.
The loudness is read in one pass without decoding the whole file into memory.
Checking against a target
The table compares the file with Spotify and YouTube (about -14 LUFS), Apple Music and podcasts (about -16 LUFS), EBU R128 broadcast (-23 LUFS, +/-0.5 LU, -1 dBTP) and ATSC A/85 (-24 LKFS, +/-2 LU, -2 dBTP). For each it shows the gain that would bring the file to the target and warns when that gain would push the true peak over the limit, which means a limiter is needed.
Streaming services normalize playback, so a louder file is turned down and nothing is "failed". Broadcast specifications are limits to meet. The values are common published figures; services change their rules, so check the current guidance for the platform you deliver to.
Next steps
To reach a target, use the loudness normalizer, which measures again after processing and applies a true-peak limiter. If the true peak is over 0 dBTP, the limiter tool or a lower volume avoids distortion when the file is encoded to MP3 or AAC.
Questions
What is the difference between LUFS and LKFS?
They are the same unit. LUFS is the name used by EBU R128 and LKFS by ATSC and the original ITU standard.
Why is my integrated loudness different from another meter?
Meters differ in gating details, the part of the file measured and rounding. Differences of a few tenths of an LU are normal; larger ones usually mean a different measurement window.
Is the true peak the same as the highest sample?
No. Between two samples the reconstructed waveform can rise above both of them. The true peak accounts for that, which is why it can read above 0 dBFS even when no sample is clipped.
Which target should I use for a podcast?
A common choice is -16 LUFS for stereo and -19 LUFS for mono with a true peak of -1 dBTP, but follow the guidance of the platform you publish on.