Turbo & Supercharger Boost Compression Calculator
Calculate Effective Compression Ratio (ECR), pressure ratio, and theoretical horsepower gain from boost.
Last reviewed by the myCalculator Editorial Team
Input Parameters
Calculation Results
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Formula & How Turbo & Supercharger Boost Compression Calculator Works
Forced induction raises the pressure of the air entering the engine, which increases the effective compression ratio. The pressure ratio is (boost + atmospheric) ÷ atmospheric, in the same units. At 12 psi of boost, the ratio is (12 + 14.7) ÷ 14.7 = 1.82. A common approximation is that the effective compression ratio is the static ratio times the square root of the pressure ratio, so a 9.5:1 engine at 12 psi behaves like 9.5 × √1.82 = about 12.8:1. A higher effective ratio makes more power but raises the risk of knock, so tuning, fuel octane and intercooling matter. Always stay within the engine manufacturer's boost and compression limits.
- Enter Static Compression Ratio (e.g. 9.5): Input your target parameter value.
- Enter Boost Pressure (PSI): Input your target parameter value.
- Enter Naturally Aspirated Base HP: Input your target parameter value.
- Apply Formula: Calculate using
Pressure Ratio = (Boost + 14.7) / 14.7 | ECR = Static CR × √Pressure Ratio. - Review Results: View exact computed answers, metrics, and worked mathematical proofs.
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MyCalculator.com.au. (2026). Turbo & Supercharger Boost Compression Calculator. Retrieved October 24, 2026, from https://www.mycalculator.com.au/calculators/engineering/engine-compression-boost
MyCalculator.com.au. (2026) 'Turbo & Supercharger Boost Compression Calculator'. Available at: https://www.mycalculator.com.au/calculators/engineering/engine-compression-boost (Accessed: 24 October 2026).
Frequently Asked Questions (FAQs)
What is Effective Compression Ratio (ECR)?
ECR is the dynamic compression ratio experienced by the engine when pressurized by a turbocharger or supercharger.
How much horsepower does 1 PSI of boost add?
As a general rule, each 1 PSI of boost adds approximately 6% to 7% more horsepower over naturally aspirated output.
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Authoritative Standards & Verified Reference Citations
Calculations and mathematical logic on this page are grounded in published statutory rules, regulatory standards, and official government data published by the following bodies:
Australian Standards including AS/NZS 3000 (Wiring Rules), AS 3600 (Concrete Structures), and AS 4100 (Steel Structures).
Accreditation and technical guidelines for civil, structural, mechanical, and electrical engineering.
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