# LUFS meter: check how loud your audio is

See a file's loudness in LUFS, its loudest peak, and its range. Always free.

## What is LUFS?

LUFS means Loudness Units relative to Full Scale. It measures how loud audio sounds to people over a whole file, weighted the way hearing works, rather than how high its peaks go. The numbers are negative because they count down from the loudest level a digital file can hold, so −14 LUFS is louder than −23. LUFS and LKFS are one scale with two names, and 1 LU is the same step as 1 dB.

The meter shows three numbers. Integrated loudness is the whole file's loudness, in LUFS. True peak is the highest point the sound reaches, even between samples, in dBTP: keep it under −1 so the file doesn't distort when it's encoded. Loudness range, in LU, is how far apart the loud and soft parts are. Everything is measured the EBU R 128 way, as broadcasters measure it.

How loud it should be depends on where it's going. Streaming services turn louder tracks down to their level, so mastering louder doesn't make you louder there.

Loudness targets, linked where they're published

| Where it's going | Loudness | Peaks | Source |
|---|---|---|---|
| Spotify | −14 LUFS (−11 on Loud, −19 on Quiet) | Under −1 dBTP, or −2 if louder than −14 LUFS | https://support.spotify.com/us/artists/article/loudness-normalization/ |
| Apple Podcasts | −16 LKFS, ±1 dB | Under −1 dB true peak | https://podcasters.apple.com/support/audio-requirements |
| YouTube | No published target: Spotify's −14 LUFS is a safe choice | Under −1 dBTP is a safe choice | Not published |
| Apple Music | No published target: Spotify's −14 LUFS is a safe choice | Under −1 dBTP is a safe choice | Not published |
| Amazon Music | No published target: Spotify's −14 LUFS is a safe choice | Under −1 dBTP is a safe choice | Not published |
| TV and radio in Europe (EBU R 128) | −23 LUFS | Under −1 dBTP | https://tech.ebu.ch/publications/r128 |
| US TV (ATSC A/85) | −24 LKFS | Under −2 dBTP | https://www.atsc.org/wp-content/uploads/2026/07/A85-2026-07.pdf |
| Audiobooks on Audible (ACX) | −23 to −18 dB average level (RMS) | Under −3 dB, with a noise floor under −60 dB | https://help.acx.com/s/article/acx-audio-submission-requirements |

Tool: Media info (`analyze_audio`). The same tool's other pages: https://audo.ai/media-info.md. Price: free, for whole files.

## Free API

```bash
curl -F file=@episode.wav https://audo.ai/api/try/media-info -D response.headers -o response.body
```

Read response.headers and response.body before naming media. Handle 202, 200 JSON and errors with the complete response client at https://audo.ai/docs/api#responses.

Always free for the whole file, 20 files a day per person. The response is the result itself; a job that runs longer than about 30 seconds returns 202 with a link to check on it. With an API key (`-H "Authorization: Bearer $AUDO_API_KEY"`), omitting free runs the whole file with credits if the balance covers it, otherwise the free portion if quota remains. Set free=true to prohibit spending; for paid whole files use free=false with an approved positive max_credits. Details: https://audo.ai/docs/api.md

## Options

Form fields with the same names as the MCP tool's inputs:

- `detail`: concise lists up to 50 silent stretches; full lists them all. Default concise.

## Languages

Any language: it works on the sound, not the words.

## From an assistant (MCP)

Add https://audo.ai/mcp and sign in (setup for each assistant: https://audo.ai/setup.md). The tool is `analyze_audio`:

> Reports a file's length, format, loudness, true peak, noise floor, silent stretches, and clipping. Use it to check a file before and after processing. Free. Answers directly for files up to an hour; longer files return a job_id for get_job.

Example: "Use Audo to check the LUFS loudness and true peak of episode.mp3."

## More

- Every tool: https://audo.ai/llms.txt
- OpenAPI: https://audo.ai/api/openapi.json
- This page for people: https://audo.ai/lufs-meter