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Compressor Gain Reduction Calculator
Calculate an ideal hard-knee compressor’s steady-state output and gain reduction from threshold, ratio and makeup gain.
Steady input level (dBFS): -120–0; Threshold (dBFS): -120–0; Ratio (input dB : 1 output dB): 1–20; Makeup gain (dB): 0–24
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Compressor Gain Reduction Calculator
Steady input level (dBFS): -6 Threshold (dBFS): -18 Ratio (input dB : 1 output dB): 4 Makeup gain (dB): 0
- Input above threshold (dB)
- 12.000000
- Output before makeup (dBFS)
- -15.000000
- Gain reduction (dB)
- 9.000000
- Output after makeup (dBFS)
- -15.000000
Enter a steady input level and threshold from −120 to 0 dBFS using the same reference, a ratio from 1:1 to 20:1, and makeup gain from 0 to 24 dB. This is an ideal downward hard-knee transfer curve, not audio processing. Above-threshold amount A=max(0,input−threshold); reduction G=A×(1−1/ratio); output before makeup=input−G; final output=input−G+makeup. Below or exactly at threshold there is no reduction. At 1:1 the compressor leaves the level unchanged before makeup. For input −6, threshold −18, ratio 4:1 and makeup 0, A=12 dB, reduction=9 dB and output=−15 dBFS. A ratio describes changes in dB above threshold, not division of the waveform amplitude. Makeup raises the entire modeled output, including signals below threshold, and does not change the reduction. Outputs are not clamped at 0 dBFS: a positive value is the algebraic model result, not a clipping or true-peak prediction. Real attack, release, knee width, detector calibration, lookahead, sidechain filtering, program dependence and parallel dry/wet mixing are excluded. Results use six decimals and can be copied, downloaded or printed with assumptions for a mix note. Confirm the actual processor’s behavior with its documentation and meters.
Methodology
How it works
Enter a steady input level and threshold from −120 to 0 dBFS using the same reference, a ratio from 1:1 to 20:1, and makeup gain from 0 to 24 dB. This is an ideal downward hard-knee transfer curve, not audio processing. Above-threshold amount A=max(0,input−threshold); reduction G=A×(1−1/ratio); output before makeup=input−G; final output=input−G+makeup. Below or exactly at threshold there is no reduction. At 1:1 the compressor leaves the level unchanged before makeup. For input −6, threshold −18, ratio 4:1 and makeup 0, A=12 dB, reduction=9 dB and output=−15 dBFS. A ratio describes changes in dB above threshold, not division of the waveform amplitude. Makeup raises the entire modeled output, including signals below threshold, and does not change the reduction. Outputs are not clamped at 0 dBFS: a positive value is the algebraic model result, not a clipping or true-peak prediction. Real attack, release, knee width, detector calibration, lookahead, sidechain filtering, program dependence and parallel dry/wet mixing are excluded. Results use six decimals and can be copied, downloaded or printed with assumptions for a mix note. Confirm the actual processor’s behavior with its documentation and meters.
Method and assumptions documented by Techrider.live
2026-10-21
Frequently asked questions
Does this predict compression on a musical signal?
No. It models one steady detector level with an ideal hard knee. Transients, detector type, timing and soft-knee behavior can produce different measured reduction.
Is makeup gain automatic loudness matching?
No. The entered gain is added after compression. This does not measure LUFS, match perceived loudness or guarantee headroom.