Loudness Meter — Free LUFS Tool
Free online loudness meter measuring Integrated LUFS, short-term and momentary loudness with K-weighting. For mixes and masters. Runs in your browser.
Protect your hearing. Start at a low volume. Never raise the volume to make a tone audible. Levels are shown in dBFS, relative to full scale — not SPL.
How it works
ITU-R BS.1770-4 K-weighting, dual-stage gating (-70 LKFS / -10 LU), and LRA computed 100% locally in your browser. No audio is ever recorded or uploaded.
Loudness normalization has revolutionized modern music consumption. By standardizing playback loudness across streaming platforms, the Loudness War has effectively been rendered obsolete.
Understanding ITU-R BS.1770-4
Standard peak meters and simple RMS meters fail to measure perceived loudness because human ears are vastly more sensitive to frequencies between $1\text{ kHz}$ and $5\text{ kHz}$ than to deep sub-bass or ultra-high treble.
The ITU-R BS.1770-4 standard solves this with:
- K-Weighting Pre-Filtering: Audio passes through a high-frequency shelf filter modeling acoustic ear resonance and a low-frequency high-pass filter modeling reduced bass sensitivity.
- 400ms Sliding Windowing: Energy is measured across $400\text{ ms}$ blocks with $75%$ overlap ($100\text{ ms}$ hop rate).
- Dual-Stage Gating:
- Absolute Gating: All blocks quieter than $-70\text{ LKFS}$ are discarded so long silent pauses do not distort the score.
- Relative Gating: Any block quieter than $10\text{ LU}$ below the absolute-gated average is discarded, ensuring soft intros or ambient decays don’t dilute the measurement of active musical sections.
$$\text{Integrated Loudness} = -0.691 + 10 \log_{10}\left(\frac{1}{|J_{\text{rel}}|} \sum_{j \in J_{\text{rel}}} p_j\right)$$
Platform Targets & Gain Offsets
| Platform | Target Loudness | Max True Peak | Normalization Mechanism |
|---|---|---|---|
| Spotify | -14 LUFS | -1.0 dBFS | Attenuates loud masters; limiters on quiet tracks |
| Apple Music | -16 LUFS | -1.0 dBFS | Sound Check attenuation; no peak limiting |
| YouTube | -14 LUFS | -1.0 dBFS | Attenuation only; will not turn quiet tracks up |
| Tidal | -14 LUFS | -1.0 dBFS | Volume leveling via metadata |
| Broadcast TV (EBU R128) | -23 LUFS | -1.0 dBFS | Strict broadcast legal requirement ($\pm 0.5$ LU) |
| Film / Netflix | -27 LUFS | -2.0 dBFS | Dialogue-gated anchor standard |
Drop your mixed or mastered track into this analyzer to check its compliance across all major streaming targets.
Frequently asked questions
What is LUFS / LKFS?
LUFS (Loudness Units relative to Full Scale) and LKFS (Loudness K-weighted relative to Full Scale) are interchangeable names for the international forensic standard (ITU-R BS.1770-4) measuring human perception of audio loudness, rather than raw electrical peak or RMS amplitude.
What is K-weighting?
K-weighting is a two-stage digital filter designed by the ITU to model how human ears perceive loudness. The first stage is a high shelf filter (+4 dB boost around 1.7 kHz) simulating acoustic head reflection and ear canal resonance. The second stage (RLB) is a steep high-pass filter that rolls off subsonic frequencies below 40 Hz which contain physical energy but little perceived loudness.
What are streaming normalization penalties?
Modern streaming services automatically match loudness levels between consecutive tracks to prevent listeners from having to constantly adjust volume. Spotify and YouTube normalize to -14 LUFS, while Apple Music normalizes to -16 LUFS. If a track is mastered to -9 LUFS, the streaming platform simply lowers its playback volume by 5 dB to 7 dB—negating the volume advantage while keeping the dynamic compression distortion.
What is Loudness Range (LRA)?
Loudness Range (measured in LU) quantifies the statistical variation in loudness over the duration of an entire track, excluding extremely quiet pauses (below -20 LU relative to track mean) and top 5% transient peaks. High LRA (12–18 LU) indicates dynamic orchestral or cinematic audio, while low LRA (3–6 LU) indicates uniform, continuous energy.