Guide
Measuring loudness in LUFS: integrated level, range and true peak
A peak meter tells you the highest instant in a file, but not how loud it sounds. Two recordings that peak at the same level can differ by ten decibels in loudness, which is why streaming services, broadcasters and podcast hosts measure in LUFS instead. The unit, loudness units relative to full scale, comes from a standard that models human hearing: it emphasises the frequencies the ear is most sensitive to and averages over time. This meter gives you the figures a mastering engineer or a podcast producer would check.
How the number is built
The audio first passes through the K-weighting filters of ITU-R BS.1770: a high-shelf boost around 1.7 kHz that models the head, and a high-pass near 38 Hz that removes low rumble. The weighted signal is cut into 400-millisecond blocks that overlap by 75%, and the mean-square power of each block is summed across channels. Blocks quieter than −70 LUFS are dropped, then blocks more than 10 LU below the average of the rest are dropped too; the power of what remains gives the integrated loudness. The filter constants are the ones in the standard, and the code is checked against its published 48 kHz coefficients.
A worked example
Press Sample to analyse a four-second stereo arpeggio. The page reports integrated loudness −14.7 LUFS, loudness range 1.7 LU and an approximate true peak of −3.6 dBFS. The highest momentary value is −13.0 LUFS and the highest short-term value −14.8 LUFS. The peak-to-loudness ratio, the true peak minus the integrated loudness, is 11.1 dB. For calibration, a full-scale 997 Hz sine on one channel measures −3.01 LUFS and the same sine on both channels reads 0.0 LUFS, as the standard specifies.
The target table
Next to the readings are four common targets. Reaching −14 LUFS needs +0.7 dB, −16 LUFS needs −1.3 dB, −23 LUFS (EBU R128 broadcast) needs −8.3 dB and −24 LUFS (the US ATSC A/85 standard for television) needs −9.3 dB. Make a copy applies that gain to the file and writes a 16-bit WAV, using a soft limiter if the gain would push peaks past full scale; the note says how many samples that touched, and you should measure the copy again. The service names are approximate: platforms change their targets, so check current guidance.
Loudness range and true peak
Loudness range (LRA) describes how much the loudness varies: a steady podcast has a few LU, a film mix or classical piece many. True peak catches the peaks that appear between samples when the signal is converted to analogue or encoded to a lossy format. The page warns when the estimate is above −1 dBTP, a ceiling many services recommend. Files under three seconds have no short-term or range value.
Edge cases
Silent files show −∞. Mono files are measured as a single channel. Very short or very quiet files may lose most blocks to the gates, so the integrated figure can be missing or unstable. The decoded rate depends on the browser for non-WAV files, which the standard allows because the filters adapt to the rate.
Limits
This is a measurement tool, not a certified compliance meter, and its true peak is an estimate. It reads the whole file at once and does not meter live input. The audio is analysed on your device.
Related tools
- Audio Volume Booster & Peak Normalizer applies gain by decibels or to a peak.
- Decibel Meter Online measures sound in the room through a microphone.
- Audio Cutter removes sections that distort a loudness reading.
- Mic Test confirms that a recording microphone is working before you measure its takes.
Checked against the current version of the LUFS Loudness Meter on .