Wheel Horsepower Calculator
Estimate wheel horsepower after drivetrain losses and compare crank versus dyno numbers for accurate performance benchmarks.
How to Use This Calculator
Enter crank horsepower
Use the manufacturer rating or estimated engine output at the flywheel.
Choose drivetrain loss
FWD cars typically lose 10-15%, RWD 15-18%, AWD 18-25% depending on driveline setup.
Optional: add RPM and dyno numbers
RPM lets us compute torque, and wheel horsepower from the dyno lets us calculate actual drivetrain loss.
Formula
Wheel HP = Crank HP × (1 − Drivetrain Loss ÷ 100)
Drivetrain Loss (hp): Crank HP − Wheel HP
Torque: Torque (lb-ft) = HP × 5252 ÷ RPM
Example: 400 hp engine, 15% loss, 6000 rpm → Wheel HP = 400 × 0.85 = 340 hp → Loss = 60 hp → Crank torque = 400 × 5252 ÷ 6000 = 350 lb-ft → Wheel torque = 340 × 5252 ÷ 6000 = 297 lb-ft.
About the Wheel Horsepower Calculator
Dyno charts show wheel horsepower, while manufacturers quote crank horsepower. This calculator bridges the gap so you can compare apples to apples and plan drivetrain upgrades.
When to Use This Calculator
- Mod planning: Estimate the wheel horsepower gain from engine upgrades.
- Dyno comparison: Translate crank claims to wheel numbers for realistic benchmarks.
- Torque estimation: Convert horsepower to torque based on RPM.
- Drivetrain design: Size clutches, axles, and differentials based on wheel torque.
Why Use Our Calculator?
- ✅ Flexible inputs: Supports optional RPM and dyno data.
- ✅ Instant conversion: Turns crank ratings into realistic wheel output.
- ✅ Torque output: Calculates wheel and crank torque for driveline sizing.
- ✅ Mobile ready: Perfect for use at the dyno or tuning shop.
Common Applications
Performance tuners: Validate horsepower gains before and after modifications.
Car enthusiasts: Compare wheel horsepower across different dynos and drivetrains.
Mechanics: Determine drivetrain components that can handle output torque.
Tips for Best Results
- Use an estimated loss range (e.g., 12–18%) to see best and worst-case wheel horsepower.
- Remember dynos have variance—compare relative gains on the same dyno when possible.
- Automatic transmissions often show higher losses than manuals; AWD is highest.
- Consider drivetrain upgrades if wheel torque exceeds component ratings.
Frequently Asked Questions
How accurate is the drivetrain loss percentage?
It’s an estimate. Use dyno data from your own vehicle when possible. Different drivetrains, tire sizes, and fluids can change loss by several percent.
Why is measured wheel horsepower optional?
Entering a dyno number lets you compute the actual loss for your specific setup. If you don’t have it, the calculation uses the estimated loss.
Does tire size affect wheel horsepower?
Indirectly. Larger, heavier tires can increase rotational inertia and drivetrain loss. Include them when evaluating dyno changes.
Can I use metric units?
Enter horsepower directly. To convert kilowatts to horsepower, multiply kW by 1.341. Torque outputs are in lb-ft; multiply by 1.356 to get N·m.