Dialnorm Calculator (AC-3 / Dolby)
Turn a measured programme loudness into the correct AC-3 dialnorm metadata value and see the attenuation a decoder will apply.
AC-3 decoders normalize every programme to −31 LKFS using the dialnorm value: a programme flagged −23 gets 8 dB of attenuation, one flagged −31 gets none. Under ATSC A/85 the dialnorm must match the real measured loudness — a mismatched value is the classic 'loud commercials' bug.
Rule / Formula
Turn a measured programme loudness into the correct AC-3 dialnorm metadata value and see the attenuation a decoder will apply.
About Dialnorm Calculator (AC-3 / Dolby)
Turn a measured programme loudness into the correct AC-3 dialnorm metadata value and see the attenuation a decoder will apply. AC-3 decoders normalize every programme to −31 LKFS using the dialnorm value: a programme flagged −23 gets 8 dB of attenuation, one flagged −31 gets none. Under ATSC A/85 the dialnorm must match the real measured loudness — a mismatched value is the classic 'loud commercials' bug.
How to use Dialnorm Calculator (AC-3 / Dolby)
- 1Enter your values into the fields in Dialnorm Calculator (AC-3 / Dolby).
- 2The result and any pass/fail verdict update instantly as you type — no button to press.
- 3Check the substituted formula and worked example to see exactly how the result was derived.
- 4Copy or note the result for your spec, delivery or planning.
Why use Dialnorm Calculator (AC-3 / Dolby)?
- ✓Runs entirely in your browser with instant, private results — no data leaves your device.
- ✓Built on a published reference: ATSC A/52 (AC-3) Annex: dialnorm semantics.
- ✓Shows the governing formula and a worked example, so you can trust and check every result.
- ✓100% free with no sign-up, no watermark and no usage limits.
- ✓Works on any device — desktop, tablet or phone — and keeps working offline once loaded.
Frequently asked questions
What does Dialnorm Calculator (AC-3 / Dolby) do?+
Turn a measured programme loudness into the correct AC-3 dialnorm metadata value and see the attenuation a decoder will apply. AC-3 decoders normalize every programme to −31 LKFS using the dialnorm value: a programme flagged −23 gets 8 dB of attenuation, one flagged −31 gets none.
Is my data private?+
Yes. Dialnorm Calculator (AC-3 / Dolby) runs entirely in your browser — your inputs are never uploaded, stored or logged.
What standard or source is Dialnorm Calculator (AC-3 / Dolby) based on?+
It follows ATSC A/52 (AC-3) Annex: dialnorm semantics; ATSC A/85:2013 §5 (metadata accuracy). Always confirm against the current official document, as specifications and rates can change.
What formula does it use?+
Dialnorm Calculator (AC-3 / Dolby) uses: dialnorm = round(measured LKFS), clamped to −1…−31; attenuation = 31 + dialnorm. The tool shows this formula with your own numbers substituted so you can verify the result.
Is Dialnorm Calculator (AC-3 / Dolby) free to use?+
Yes — it is completely free with no account, no sign-up and no usage limits. There is no watermark and no paywall.
Embed Dialnorm Calculator (AC-3 / Dolby) on your website
Want Dialnorm Calculator (AC-3 / Dolby)on your own site? Paste this snippet into any HTML page — it's free, with no API key or sign-up. The tool loads in an iframe and keeps working exactly as it does here.
<iframe src="https://tooljolt.com/tools/dialnorm-calculator" width="100%" height="640" style="border:1px solid #e5e7eb;border-radius:12px;max-width:680px" title="Dialnorm Calculator (AC-3 / Dolby) — ToolJolt" loading="lazy"></iframe>Related Broadcast tools
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