🏎️ Turbo & supercharger tool

Boost Horsepower Calculator

Estimate how much horsepower a turbo or supercharger setup may add. Calculate boosted horsepower, boost needed for a target horsepower, pressure ratio, airflow estimate, fuel flow, injector size, and realistic wheel horsepower after drivetrain loss.

Core formulaHP ≈ Base HP × PR × Efficiency

PR means pressure ratio. This is a planning estimate, not a dyno tune.

Calculator

Base horsepower HPNaturally aspirated or current engine horsepower. Boost pressure PSIGauge boost pressure above atmospheric pressure. System efficiency %Typical planning range: 70–90%. Atmospheric pressure PSISea level is about 14.7 PSI. Drivetrain loss %Estimate wheel horsepower after drivetrain loss. Fuel type BSFCFuel used per HP per hour. Injectors countUsually one injector per cylinder. Max duty cycle %Leave safety room below 100%. Static compression :1Used for effective compression estimate.

Estimated boosted horsepower

394 HP

250 HP × 1.68 pressure ratio × 85% efficiency.

⚠️ Estimate only

Power gain+144 HP+57.8%

Pressure ratio1.68Absolute pressure ratio

Wheel HP335 WHPAfter drivetrain loss

Injector size695 cc/minper injector estimate

Quick build presets

How the boost horsepower calculator works

This calculator estimates forced-induction horsepower from base horsepower, boost pressure, atmospheric pressure, and system efficiency. It is useful for planning turbocharger or supercharger builds, comparing boost levels, and checking whether the fuel system may support the target power.

Pressure ratio: PR = (Atmospheric PSI + Boost PSI) ÷ Atmospheric PSI
Boosted horsepower: HP = Base HP × PR × Efficiency
Boost needed: PSI = Atmospheric PSI × ((Target HP ÷ Base HP ÷ Efficiency) − 1)
Injector size: lb/hr = (HP × BSFC) ÷ (Injectors × Duty Cycle)

Example

If an engine makes 250 HP naturally aspirated, runs 10 PSI boost, and the setup is 85% efficient, the pressure ratio is about 1.68. Estimated boosted power is roughly 250 × 1.68 × 0.85 = 357 HP. Real dyno results can differ because of heat, tuning, compressor efficiency, fuel quality, backpressure, intercooling, and engine condition.

Safety note: This is an educational planning calculator. Always tune boosted engines with proper fuel, ignition timing, knock monitoring, wideband oxygen readings, and a qualified tuner.

Why efficiency matters

A perfect pressure-ratio calculation assumes ideal airflow and temperature. Real systems lose power through heat, intake restriction, exhaust backpressure, compressor efficiency, intercooler pressure drop, belt drag on superchargers, and conservative timing.

Extra features included

Target mode: Enter desired horsepower and estimate required PSI.
Fuel estimate: Estimate fuel flow and injector size using BSFC and duty cycle.
Wheel horsepower: Apply drivetrain loss to estimate WHP.
Effective compression: Estimate how boost changes engine pressure load.
History and sharing: Copy or share your latest estimate.

Boost horsepower table

Boost PSI	Pressure ratio	250 HP @ 85%	350 HP @ 85%

FAQs

Boost horsepower is the estimated horsepower after a turbocharger or supercharger increases intake air pressure. More air can support more fuel and more power when tuned correctly.

No. It is a planning estimate. Real power depends on compressor maps, intake temperature, intercooler efficiency, fuel, timing, exhaust flow, engine health, and dyno conditions.

Yes. The pressure-ratio method works as a broad estimate for both. Superchargers may have extra parasitic losses, so use a lower efficiency if needed.

For rough planning, 70–90% is common. Use lower values for hot, restrictive, or less optimized setups and higher values for well-matched, intercooled systems.

No. Injector size is only one part of the fuel system. Pump flow, fuel pressure, wiring, regulator, fuel type, and professional tuning also matter.