The US CALM Act (enacted 15 December 2010, FCC rules effective 13 December 2012) requires TV commercials to be transmitted no louder than the programme material they accompany; the FCC rules incorporate ATSC A/85 by reference, whose core requirement is that the average loudness of a commercial must not exceed the average loudness of the surrounding programming. This checker measures both files the way the standard does: ITU-R BS.1770-4 K-weighted integrated loudness with the two-stage EBU Mode gate, taken over the full duration including all channels except LFE (A/85 Annex J.4). For long-form programmes A/85 anchors on the dialogue element; this tool measures the full-program mix, so for cinematic mixes you can instead enter the known anchor or dialnorm value directly. The loudness difference is graded on the A/85 Annex E listener tolerance scale: +2.4 dB is louder-but-acceptable, +5.6 dB makes viewers reach for the volume control, +10.8 dB is annoyingly loud, while a commercial up to +2 dB over the programme sits inside the A/85 measurement tolerance. True peak of the commercial is checked against the A/85 −2.0 dBTP limit, and because the FCC’s 2025 review highlights commercials that “game” the average with an exceptionally loud opening, the maximum momentary (400 ms) loudness of the commercial is compared with the programme’s as an informational diagnostic. Files are only read, never modified.