How loudness compliance works
Modern broadcast and streaming standards specify a single target value for programme integrated loudness measured per ITU-R BS.1770 - a "K-weighted" energy average across the whole programme. Engineers measure the integrated value with a loudness meter (in their DAW or encoder), compare it to the target, and apply a flat gain.
gain_dB = target_LUFS - measured_LUFS
true_peak_after = measured_true_peak + gain_dB
// 1 LU = 1 dB exactly
True-peak headroom
True-peak (dBTP) is the highest inter-sample peak after upsampling. Each standard sets a maximum (-1 dBTP for streaming, -2 dBTP for ATSC A/85 and Netflix) to prevent clipping in downstream DAC and codec stages. If applying a +N dB gain pushes true-peak above the ceiling, you need to limit rather than just gain - or accept losing dynamic range.
Loudness target reference
| Standard | Target | Tolerance | True-peak ceiling | Notes |
|---|---|---|---|---|
| EBU R128 | -23 LUFS | ±1 LU | -1 dBTP | European broadcast |
| ATSC A/85 | -24 LKFS | ±2 LU | -2 dBTP | US broadcast (CALM Act) |
| Apple Sound Check | -16 LUFS | ±2 LU | -1 dBTP | Music / podcast (varies, verify) |
| Spotify | -14 LUFS | ±2 LU | -1 dBTP | Loudness-normalised music streaming |
| YouTube | -14 LUFS | ±2 LU | -1 dBTP | Auto-normalised (varies, verify) |
| Amazon | -14 LUFS | ±2 LU | -2 dBTP | Music; video may differ |
| Netflix Originals | -27 LKFS | ±2 LU | -2 dBTP | Dialogue-anchored (sound mix) |
Streaming-platform targets evolve; always verify against the latest delivery spec before mastering. The broadcast values (R128, A/85) are stable and codified.
Frequently Asked Questions
What is LUFS vs LKFS?
LUFS (Loudness Units Full Scale) and LKFS (Loudness, K-weighted, relative to Full Scale) are numerically identical. EBU uses "LUFS"; ATSC and ITU-R BS.1770 use "LKFS". -23 LUFS = -23 LKFS.
What is the EBU R128 loudness target?
Programme integrated loudness of -23 LUFS with ±1 LU tolerance, a maximum loudness range (LRA), and a max true-peak of -1 dBTP.
What is the ATSC A/85 loudness target?
Programme integrated loudness of -24 LKFS with ±2 LU tolerance and a max true-peak of -2 dBTP. The US broadcast standard codified by the CALM Act.
How do I calculate the gain to reach a loudness target?
gain_dB = target_LUFS - measured_LUFS. 1 LU equals 1 dB, so apply the result as a flat gain. Example: measured -18 LUFS, target -23 LUFS → -5 dB (cut). Always re-measure after limiting.