Engine Compression Ratio Calculator
Calculate audio compressor output levels from threshold, ratio, and input level. Visualize gain reduction for mixing and mastering.
Specialist tool for Auto Mod1 documented formulaFocused single-task workflowPrivate in your browser
Use this result well
A quick decision brief for this specific tool
Inputs that matter
Swept Volume (per cylinder), Clearance Volume (TDC)
Output to expect
Compression Ratio Calculator
How it works
1 documented formula across 1 calculation mode
- Confirm that every value uses the unit and time basis shown before comparing scenarios.
- Change one input at a time to see which assumption materially changes the result.
Was this tool helpful?
Related Tools
Tools you might need next
Audio Compression Ratio Calculator
Calculate compressor output level above threshold for a given ratio. Free audio compression ratio calculator for studio recording, mixing, and live sound.
Music Audio
Compression Ratio Calculator
Calculate audio compressor output levels from threshold, ratio, and input level. Visualize gain reduction for mixing and mastering.
Music Production
Model Compression Ratio
Calculate compression ratio and size savings from quantization or pruning. Free online data science calculator with instant, accurate results.
Data Science
Reference & details
How it works
Updated July 2026
How it works
Updated July 2026Gain Reduction
When input exceeds threshold, excess level is reduced by ratio. 4:1 ratio means 4 dB input above threshold produces 1 dB output above threshold.
GR = (Input − Threshold) × (1 − 1/Ratio)Output Level
Below threshold, output equals input (no compression). Above threshold, output increases at 1/ratio of the rate input increases.
Output = Input − GR (when Input > Threshold)Makeup Gain
Apply makeup gain to restore perceived loudness after compression. Typical: match peak or RMS level to uncompressed signal.
Output_final = Output + Makeup gainUpdated: July 2026
Example Scenarios
Input peaks 10 dB above −20 dBFS threshold → 7.5 dB gain reduction. Peaks compressed from +10 to +2.5 dB relative to threshold.
Light 2:1 on drum bus with −10 dB threshold tames transients without audible pumping — 3 dB GR on loudest hits.
Effectively brick-wall above threshold. Input 5 dB over threshold with 20:1 → 4.75 dB GR, output only 0.25 dB above threshold.
FAQ
2:1 for gentle leveling (bass, mix bus). 4:1–6:1 for vocals and instruments. 8:1–20:1 for limiting and aggressive control. Higher ratio = more compression.
Input level above which compression begins. Set threshold so compressor engages on loudest passages you want to control, not on entire signal.
Soft knee gradually increases ratio near threshold (smooth transition). Hard knee applies full ratio immediately at threshold. Soft knee sounds more transparent.
For transparent compression: 3–6 dB GR on peaks. 10+ dB GR is audible and stylistic. Constant 6+ dB GR suggests threshold too low or ratio too high.
Ratio calculation is steady-state. Attack determines how fast compression engages; release how fast it disengages. They affect perceived compression, not the ratio math.
About Engine Compression Ratio Calculator
Audio compressors reduce dynamic range by attenuating signals above a threshold. Enter input level, threshold, ratio, and knee settings to calculate output level, gain reduction in dB, and effective compression for mixing decisions.