Boost Horsepower Calculator
Estimate how much power your engine can make when you add boost using turbos or superchargers.
How to Use This Calculator
Start with your baseline power
Enter naturally aspirated horsepower or the current output before adding boost.
Enter your target boost level
Boost pressure is typically measured in psi at the intake manifold.
Verify ambient pressure
At sea level use 14.7 psi. Reduce it slightly for high-elevation builds.
Set your volumetric efficiency
Use 100% for a well-tuned setup. Reduce to 90–95% for typical street builds.
Formula
Boosted HP = Base HP × ((Boost + Ambient) ÷ Ambient) × η
Where: Boost and ambient pressure are in psi, and η (eta) is volumetric efficiency as a decimal.
Example with 250 hp baseline, 10 psi boost, 14.7 psi ambient, and 95% efficiency:
Pressure ratio = (10 + 14.7) ÷ 14.7 = 1.68
Boosted HP = 250 × 1.68 × 0.95 = 399 hp
About the Boost Horsepower Calculator
Forced induction packs more air into the combustion chamber, allowing the engine to burn more fuel and generate greater power. This calculator estimates the theoretical output of an engine when subjected to a target boost pressure.
When to Use This Calculator
- Planning a turbo build: Understand potential power levels before ordering components.
- Supercharger upgrades: Compare pulley combinations and boost curves.
- Dyno result validation: Sanity-check measured horsepower from chassis dynamometers.
- Altitude adjustments: Estimate power loss or gain when racing at different elevations.
Why Use Our Calculator?
- ✅ Quick experimentation: Change boost or efficiency and immediately see the impact.
- ✅ Realistic efficiency factor: Account for intercooler performance and heat soak.
- ✅ Baseline comparison: Outputs both net gain and percentage increase.
- ✅ Mobile-ready: Perfect for planning while you're at the shop or track.
Common Applications
Engine swaps: Predict final horsepower when adapting turbocharged engines into new chassis.
Tuning sessions: Set realistic goals before scheduling dyno time or street tuning.
Budget planning: Determine if supporting mods like fuel upgrades are necessary.
Tips for Best Results
- Measure boost at the intake manifold, not at the compressor outlet.
- Use lower efficiency values for hot climates or restrictive intercoolers.
- Remember that drivetrain losses mean wheel horsepower will be lower than crank horsepower.
- Stay within the safe limits of your engine internals and fueling system.
Frequently Asked Questions
Does this calculate crank or wheel horsepower?
The result reflects crankshaft horsepower. To estimate wheel horsepower, multiply by your drivetrain efficiency (e.g. 0.85 for rear-wheel-drive).
Why include volumetric efficiency?
Efficiency captures real-world factors like intercooler effectiveness, intake restrictions, and camshaft timing. Without it, the estimate would be overly optimistic.
Can I use this for compound or twin-turbo setups?
Yes. As long as you know the total manifold boost pressure, the pressure ratio model still applies.
What if my engine has variable boost?
Run the calculation at different boost levels to see how output changes across the map. This is helpful when using electronic boost control.