Enter your engine's naturally aspirated horsepower, boost pressure (psi), and atmospheric pressure to calculate your boosted horsepower after adding a supercharger or turbocharger. You'll see your power gain and total boosted output side by side, with a visual breakdown of stock vs. boosted power.
Boosted Horsepower (Crank)
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Power Gain
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Boost Multiplier
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Estimated Wheel Horsepower
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Stock Wheel Horsepower
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A supercharger compresses the intake air, forcing more air (and thus more fuel) into the engine's cylinders than atmospheric pressure alone would allow. This denser air-fuel mixture produces a larger combustion event with each stroke, resulting in higher power output. The supercharger is belt-driven by the engine itself, so it produces boost at all RPM ranges, even from idle.
The calculator uses the standard boost HP formula: Boosted Power = ((Atmospheric Pressure + Boost Pressure) / Atmospheric Pressure) × Naturally Aspirated Horsepower. At sea level, atmospheric pressure is 14.7 psi, so each pound of boost increases airflow proportionally. For example, 14.7 psi of boost (doubling absolute pressure) would theoretically double your engine's output.
Gauge pressure (what your boost gauge reads) measures pressure above atmospheric pressure. Absolute pressure is gauge pressure plus atmospheric pressure (14.7 psi at sea level). The boost HP formula uses absolute pressure, which is why atmospheric pressure appears in both the numerator and denominator. Our calculator handles this conversion automatically.
A supercharger is mechanically driven by the engine's crankshaft via a belt, providing instant boost response at any RPM. A turbocharger is exhaust-driven, using spent gases to spin a turbine that compresses intake air — this makes it more efficient but introduces 'turbo lag' before boost builds. Both increase power by forcing more air into the engine, and the boost HP formula applies equally to both.
Yes. At higher altitudes, atmospheric pressure is lower than the sea-level standard of 14.7 psi. This means your engine starts with less ambient air, so both your naturally aspirated baseline and your boosted output will be lower. You can adjust the Atmospheric Pressure field in our calculator to reflect your actual altitude — for example, roughly 12.2 psi at 5,000 feet.
Crank horsepower (also called brake horsepower) is the power produced at the engine's crankshaft, before any drivetrain losses. Wheel horsepower is what's measured at the driven wheels after power is lost to the transmission, driveshaft, and differentials. Typical drivetrain losses range from 15% for rear-wheel drive vehicles to 20% or more for all-wheel drive systems.
This calculator provides a theoretical estimate based on ideal gas behavior and the standard boost pressure formula. Real-world results may differ due to factors like engine volumetric efficiency, intercooler effectiveness, parasitic losses from the supercharger itself, air temperature, and fuel delivery limitations. Use this as a planning guide rather than a precise dyno replacement.
Most factory-fitted and mild aftermarket supercharger kits for street use run between 6 and 12 psi of boost. High-performance and race applications can run 15–25 psi or more, but these typically require upgraded internals, fuel systems, and engine management. Running excessive boost on an unmodified engine risks detonation and serious engine damage.