Boost Horsepower Calculator — Turbo / Supercharger HP Estimator
Enter your engine's naturally-aspirated horsepower, the boost pressure your turbocharger or supercharger produces, and an efficiency factor to estimate the power at the wheels or crank with forced induction.
hp
Boost unit
%
Estimated wheel/crank HP with forced induction at the given boost and efficiency
- 1
Absolute intake pressure
14.696 + 10 = 24.696Atmospheric pressure (14.696 psi at sea level) plus gauge boost pressure. - 2
Pressure ratio
24.696 ÷ 14.696 = 1.6805 - 3
Estimated boosted HP
200 × 1.6805 × 0.88 = 296Base HP scaled by the pressure ratio, then derated by the mechanical efficiency factor.
How does this calculator work?
HP_boosted = HP_base × ((14.7 + boost_psi) / 14.7) × η. At 10 psi boost and 88% efficiency a 200 hp engine gains roughly 119 hp to reach ~319 hp. The pressure ratio shows how much more air the engine receives; multiply by efficiency to account for real-world losses.
Formula
How this is calculated
A turbocharger or supercharger forces more air into the engine than it could draw naturally, allowing more fuel to be burned per cycle and producing proportionally more power. The baseline relationship is straightforward: power scales with absolute air pressure. If you double the absolute pressure in the intake manifold, you roughly double the power output (assuming the engine can handle the additional stress and fuelling is matched).
Absolute pressure is gauge boost pressure plus atmospheric pressure (14.696 psi at sea level). The power ratio is P_absolute / P_atmospheric. A real engine and drivetrain are not perfectly efficient, however — intercooler pressure drops, plumbing losses, compressor heat, and mechanical parasitic drag all reduce the actual gain. The efficiency factor (η) bundles all of these real-world losses into one editable number; 88% is a reasonable midpoint for a well-set-up street application.
This formula gives an estimate for planning and comparison purposes. Actual power depends heavily on engine internals, fuelling, ignition timing, temperature, altitude, and the specific compressor map. Always verify results on a calibrated dynamometer after any forced-induction modification.
Frequently asked questions
It is a good linear approximation at moderate boost levels (up to about 20 psi / 1.4 bar). At higher boost the air-fuel ratio, intercooler efficiency and engine breathing become non-linear factors that simple pressure-ratio math does not capture. Use a dyno to confirm actual power at high boost.
A typical range is 85–95%. Use 85–88% for an older setup with a hot side before a smaller intercooler; 90–95% for a top-spec race intercooler and low-restriction plumbing. If in doubt, 88% is a conservative real-world default for a street build.
Yes. Atmospheric pressure at altitude is lower than 14.7 psi, so your turbo must work harder to reach the same absolute manifold pressure. A turbocharger can compensate for altitude better than a supercharger because it is driven by exhaust energy rather than the engine directly. This calculator uses sea-level atmospheric pressure; reduce base HP by roughly 3% per 1,000 ft of elevation before entering it.
TG we-Calculate Editorial Team. (2026). Boost Horsepower Calculator — Turbo / Supercharger HP Estimator [Online calculator]. TG we-Calculate. https://we-calculate.com/calculator/boost-horsepower-calculator
TG we-Calculate Editorial Team. "Boost Horsepower Calculator — Turbo / Supercharger HP Estimator." TG we-Calculate. 2026. https://we-calculate.com/calculator/boost-horsepower-calculator.
TG we-Calculate Editorial Team, "Boost Horsepower Calculator — Turbo / Supercharger HP Estimator," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/calculator/boost-horsepower-calculator
@misc{wecalculate_boost_horsepower_calculator, title = {Boost Horsepower Calculator — Turbo / Supercharger HP Estimator}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/calculator/boost-horsepower-calculator}}, year = {2026}, note = {TG we-Calculate} }
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