Loudness Units relative to Full Scale – the standardized measurement unit for perceived audio loudness according to ITU-R BS.1770, used worldwide for broadcast compliance, streaming platform specifications, and professional audio production to ensure consistent listening experiences.
What is LUFS?
LUFS (Loudness Units relative to Full Scale) is the standardized unit for measuring perceived audio loudness according to ITU-R BS.1770. LUFS is identical to LKFS and forms the basis for all modern loudness standards.
Basic Principle
| Aspect | Description |
|---|---|
| Definition | Perceived Loudness |
| Standard | ITU-R BS.1770 |
| Equivalent | LKFS (identical) |
| Reference | 0 dBFS = 0 LUFS |
LUFS vs. LKFS
| Aspect | LUFS | LKFS |
|---|---|---|
| Meaning | Loudness Units FS | Loudness K-weighted FS |
| Standard | EBU | ITU/ATSC |
| Value | Identical | Identical |
| Region | Europe preferred | USA preferred |
Measurement Process
| Component | Description |
|---|---|
| K-Weighting | Frequency Curve |
| Channel Weighting | Surround Adjustment |
| Gating | Exclude Silence |
| Integration | Temporal Averaging |
K-Weighting Curve
| Frequency | Adjustment |
|---|---|
| < 100 Hz | Reduced |
| 100-2000 Hz | ~Neutral |
| 2-4 kHz | +4 dB Shelf |
| > 4 kHz | +4 dB (boosted) |
Measurement Types
| Type | Time Window | Application |
|---|---|---|
| Momentary | 400 ms | Real-time Monitoring |
| Short-term | 3 seconds | Short Passages |
| Integrated | Full Program | Compliance |
Target Values by Platform
| Platform | LUFS | True Peak |
|---|---|---|
| Netflix | -27 (±2) | -2 dBTP |
| Amazon | -24 | -2 dBTP |
| Spotify | -14 | -1 dBTP |
| YouTube | -14 | -1 dBTP |
| Apple Music | -16 | -1 dBTP |
| Broadcast EU | -23 (±1) | -1 dBTP |
| Broadcast US | -24 | -2 dBTP |
EBU R128 Standard
| Parameter | Value |
|---|---|
| Target | -23 LUFS |
| Tolerance | ±1 LU |
| True Peak | -1 dBTP |
| LRA | Recommended |
ATSC A/85 Standard
| Parameter | Value |
|---|---|
| Target | -24 LKFS |
| Tolerance | ±2 LU |
| True Peak | -2 dBTP |
| Dialnorm | Metadata |
Gating Explained
| Gate | Function |
|---|---|
| Absolute Gate | -70 LUFS (Silence) |
| Relative Gate | -10 LU below Ungated |
| Combination | Standard BS.1770-4 |
| Purpose | Relevant Material Only |
Loudness Range (LRA)
| Value | Interpretation |
|---|---|
| < 5 LU | Highly Compressed |
| 5-10 LU | Pop, Rock |
| 10-15 LU | Film Average |
| > 15 LU | Very Dynamic |
True Peak
| Aspect | Description |
|---|---|
| Measurement | Oversampling (4x+) |
| Unit | dBTP |
| Purpose | Inter-Sample Peaks |
| Headroom | For Codecs |
Measurement Tools
| Tool | Description |
|---|---|
| Youlean Loudness | Free, Precise |
| WLM Plus (Waves) | Industry Standard |
| Nugen VisLM | Professional |
| iZotope Insight | Comprehensive |
DAW Integration
| DAW | Metering |
|---|---|
| Pro Tools | Integrated |
| Nuendo | Supervision |
| Logic Pro | Loudness Meter |
| DaVinci Resolve | Fairlight |
Workflow
| Step | Action |
|---|---|
| 1 | Create Mix |
| 2 | Measure Integrated |
| 3 | Calculate Difference |
| 4 | Adjust Gain |
| 5 | Check True Peak |
Practical Calculation
| Measurement | Target | Adjustment |
|---|---|---|
| -20 LUFS | -24 LUFS | -4 dB |
| -28 LUFS | -24 LUFS | +4 dB |
| -24 LUFS | -24 LUFS | 0 dB |
Common Mistakes
| Mistake | Problem |
|---|---|
| Measuring Peak Only | Loudness Ignored |
| Momentary Instead of Integrated | Incorrect Reference |
| Forgetting True Peak | Codec Issues |
| No Tolerance | Too Strict |
Streaming Normalization
| Behavior | Description |
|---|---|
| Quieter than Target | Will Be Raised |
| Louder than Target | Will Be Lowered |
| Within Range | Unchanged |
| Consequence | Louder ≠ Better |
Cinema Context
| Aspect | Value |
|---|---|
| Dialog Normalization | -31 LKFS |
| Reference Level | 85 dB SPL |
| Measurement | Dialog-Based |
| Standard | Dolby |
Quality Control
| Check | Criterion |
|---|---|
| Integrated | Within Tolerance |
| True Peak | Below Maximum |
| Short-term | No Outliers |
| LRA | Appropriate |
Best Practices
| Practice | Reason |
|---|---|
| Know Target Value | Platform-Specific |
| Prioritize Integrated | Overall Picture |
| Consider True Peak | Codec Safety |
| Utilize Tolerances | Don't Over-Optimize |
Today
LUFS has established itself as the universal unit for loudness measurement. From broadcast to streaming to cinema – LUFS/LKFS are the common language for consistent audio quality. Understanding this measurement is fundamental for anyone working professionally with audio.