Free horsepower calculator
Enter any two of torque, RPM, or horsepower — this horsepower calculator solves for the third using the SAE formula hp = torque × RPM ÷ 5,252, updated live, as you type.
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hp = torque × RPM ÷ 5252. 1 mechanical horsepower = 0.7457 kW (SAE).
Results are estimates. Consult a professional.
How the horsepower calculator works
Horsepower and torque are two sides of the same coin. Horsepower measures the rate at which an engine does work — it tells you how fast power is delivered over time. Torque measures the rotational force at the crankshaft. The two are mathematically linked by engine speed (RPM), and the constant 5,252 ties them together at every point on a power curve.
One mechanical horsepower equals 550 foot-pounds per second, or 745.7 watts. The metric equivalent — the PS or CV (Pferdestärke / cheval-vapeur) — is defined as 75 kilogram-metres per second, equaling 735.5 watts, about 1.4% less than a US mechanical horsepower. Because the conversion constant is fixed at 5,252, torque and horsepower curves always intersect at exactly 5,252 RPM on any dynamometer chart.
SAE J1349: Engine Power Test Code — Spark Ignition and Compression IgnitionWorked example: Corvette Z06 at peak torque
A naturally aspirated 5.5-liter flat-plane V8 produces 470 lb-ft of torque at 6,000 RPM. What is the peak power output at that engine speed?
Horsepower and torque for well-known vehicles
The table below lists crank (flywheel) horsepower and peak torque for a range of well-known production and motorsport vehicles. All figures are manufacturer-rated at the crankshaft; wheel horsepower will be 10–20% lower due to drivetrain losses.
| Vehicle | Crank HP | Peak Torque (lb-ft) | Peak Power RPM |
|---|---|---|---|
| Economy car (Honda Civic 2.0L) | 158 | 138 | 6,500 |
| Muscle car (Ford Mustang GT) | 486 | 418 | 7,000 |
| Supercar (Chevrolet Corvette Z06) | 670 | 460 | 8,400 |
| Hypercar (Bugatti Chiron) | 1,479 | 1,180 | 6,700 |
| Pickup truck (Ram 1500 TRX) | 702 | 650 | 6,100 |
| Sport motorcycle (Kawasaki Ninja H2R) | 310 | 124 | 14,000 |
| F1 car (2023 hybrid PU, est.) | ~1,000 | ~443 | ~12,000 |
Sources: Manufacturer press releases and SAE J1349 certified dyno sheets. F1 PU output is an industry estimate.
Tips for interpreting horsepower numbers
Manufacturer horsepower claims can be misleading if you don't know how and where the measurement was taken. Use these tips to compare figures accurately.
- Crank vs. wheel HP — Advertised horsepower is always at the crankshaft. Expect 10–20% loss through the transmission, driveshaft, and differential before power reaches the wheels. A front-wheel-drive car loses the least; a 4WD truck the most.
- SAE net vs. gross — Post-1971 US ratings use SAE net (engine fully dressed with all accessories), which is lower than the old SAE gross method. Don't compare pre-1972 gross figures to modern net figures directly.
- The 5,252 RPM crossover — On any dyno chart, torque and horsepower lines always cross at 5,252 RPM. Below that point, torque exceeds horsepower numerically; above it, horsepower is the higher number.
- Metric HP (PS) conversion — European cars often quote PS (pferdestärke). Multiply by 0.9863 to convert to US mechanical horsepower (1 PS = 735.5 W; 1 US hp = 745.7 W).
- Altitude derating — Naturally aspirated engines lose roughly 3% power per 1,000 feet of elevation above sea level. Turbocharged engines maintain boost pressure and are much less affected.
Accuracy and limitations
This calculator uses the exact SAE J1349 formula and produces mathematically precise results. The inputs, however, depend on the accuracy of your torque and RPM source data. Manufacturer-published figures are tested under ideal lab conditions (standard temperature, pressure, and humidity) and may not reflect real-world engine output in your vehicle's operating environment.
Dynamometer measurements vary between facilities depending on equipment calibration, ambient conditions, and whether corrections are applied (SAE, DIN, or uncorrected). Chassis dyno readings are particularly variable: a 15–20% drivetrain loss is typical, but all-wheel-drive vehicles measured on a 2WD dyno will show artificially low numbers. Always compare dyno sheets from the same facility and correction standard for meaningful results.
Horsepower and torque terms defined
About this horsepower calculator
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