True-Peak Limiter Ceiling & Intersample Overs Calculator
Calculate recommended limiter ceiling levels, inter-sample peak (ISP) overshoot margins, and DAC reconstruction safety across Spotify, Apple Music, YouTube, and Broadcast TV specifications.
1. Target Delivery Standard
2. Limiter Ceiling & ISP Risk Verdict
Understanding Intersample Peaks & True-Peak Limiting
A digital sample meter (dBFS) measures only discrete digital numbers. However, when digital audio is converted into analog soundwaves by a Digital-to-Analog Converter (DAC), the continuous wave reconstructed between two sample points can arc higher than the individual points themselves:
- Why -0.1 dBFS Digital Ceilings Fail: If two consecutive samples sit at -0.1 dBFS, the reconstructed analog wave between them often peaks at +0.5 dB to +1.5 dB, causing harsh clipping in consumer DACs and smartphone speakers.
- The Lossy Transcoding Trap: When streaming platforms encode your 24-bit WAV file into lossy AAC, Ogg Vorbis, or MP3 formats, the lossy psychoacoustic compression alters transient peak phase, boosting peak levels by +0.3 dB to +0.8 dB.
- The -1.0 dBTP Gold Standard: Setting your true-peak limiter ceiling to -1.0 dBTP (or -2.0 dBTP for hot EDM masters) guarantees that inter-sample overshoots and lossy transcode boosts never clip above 0 dBFS.
Worked examples: ceilings, targets and encoder overshoot
The tool does not change your audio. It reports the ceiling and loudness target for the delivery you pick, then estimates how far the encoder pushes the peaks back up. These are the targets it shows for each delivery option:
| Delivery | Ceiling | Loudness target |
|---|---|---|
| Spotify or Apple Music streaming | -1.0 dBTP | -14.0 LUFS |
| Spotify with hyper-compressed material | -2.0 dBTP | -14.0 LUFS |
| YouTube video audio | -1.0 dBTP | -14.0 LUFS |
| Broadcast television, EBU R128 | -1.0 dBTP | -23.0 LUFS |
| Broadcast television, ATSC A/85 | -2.0 dBTP | -24.0 LUFS |
| Apple Digital Masters | -1.0 dBTP | -16.0 LUFS |
| Club or Red Book CD | -0.3 dBTP | -9.0 to -6.0 LUFS |
The overshoot is the tool's own estimate. It assumes 0.4 dB for AAC and Ogg Vorbis, 0.8 dB for MP3 at 128 kbps and 0.1 dB for an uncompressed file, and adds 0.3 dB for hyper-compressed material. The tool adds that figure to the ceiling you entered. A result above 0 dB is a clipping risk, a result between -0.2 and 0 dB is borderline, and anything lower has headroom. With a starting ceiling of -1.0 dBTP:
| Format | Material | Your ceiling | Estimated overshoot | Result |
|---|---|---|---|---|
| AAC 256 kbps | medium | -1.0 dBTP | +0.4 dB | Clean headroom, -0.6 dB |
| AAC 256 kbps | hyper-compressed | -1.0 dBTP | +0.7 dB | Clean headroom, -0.3 dB |
| MP3 128 kbps | medium | -1.0 dBTP | +0.8 dB | Borderline margin |
| MP3 128 kbps | hyper-compressed | -1.0 dBTP | +1.1 dB | High clipping risk, +0.10 dB |
| MP3 128 kbps | medium | -2.0 dBTP | +0.8 dB | Clean headroom, -1.2 dB |
| WAV or FLAC | medium | -1.0 dBTP | +0.1 dB | Clean headroom, -0.9 dB |
| AAC 256 kbps | medium | 0.0 dBTP | +0.4 dB | High clipping risk, +0.40 dB |
The first two rows show why the hyper-compressed option exists. The same -1.0 dBTP ceiling leaves 0.6 dB of headroom on medium material and 0.3 dB on hyper-compressed material. MP3 at 128 kbps is the stricter case. A -1.0 dBTP ceiling is already borderline for medium material and slips into clipping risk for hyper-compressed material, which is why the fifth row drops the ceiling to -2.0 dBTP and restores 1.2 dB. The last row shows the cost of leaving a limiter at 0 dB.
Working Vocabulary
Key audio mastering and loudness metering terms:
- True-Peak (dBTP). A metering measurement standardized by ITU-R BS.1770 that uses 4x oversampling to detect continuous inter-sample peaks between discrete digital samples.
- Inter-Sample Peak (ISP). An analog waveform peak that exceeds digital full scale (0 dBFS) during digital-to-analog reconstruction even when individual sample points remain below 0 dBFS.
- LUFS (Loudness Units Full Scale). The international standard for measuring perceived audio loudness over time.
- Crest Factor. The decibel ratio between the peak level and the RMS/average level of an audio waveform.