Engine Horsepower Calculator

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Elapsed Time (ET) Method

Estimates engine horsepower using vehicle weight and the elapsed time to finish a quarter mile (402.3 m) drag race. Formula: HP = Weight ÷ (ET ÷ 5.825)³

Vehicle Weight

Include driver, passengers, and cargo weight

Quarter Mile Elapsed Time (ET)

Time from start to finish the quarter mile

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Trap Speed Method

Estimates engine horsepower using vehicle weight and the speed at the end of a quarter mile. Formula: HP = Weight × (Speed ÷ 234)³

Vehicle Weight

Include driver, passengers, and cargo weight

Trap Speed (at quarter mile)

Speed when crossing the quarter-mile finish line (not average speed)

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Torque & RPM Method

Calculate engine horsepower from dyno-measured torque and RPM. Formula: HP = (Torque × RPM) ÷ 5,252. Also solve for Torque or RPM if HP is known.

Engine Torque

Peak torque from dyno or manufacturer spec

Engine Speed (RPM)

RPM at which peak power is produced

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Electric Motor Horsepower

Calculate horsepower of an electric motor from its voltage, current draw, and efficiency. Formula: HP = (V × I × Eff) ÷ 746

Voltage (V)

Motor operating voltage (e.g. 400V for EV)

Current (Amps)

Motor current draw at peak power

Efficiency (%)

Motor efficiency (typically 85–97% for EV motors)

Motor Type

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Power-to-Weight Ratio

Calculate your vehicle's power-to-weight ratio, estimated 0-60 mph time, and see how it compares to famous production vehicles.

Engine Horsepower

Rated wheel horsepower (whp) or crank hp

Vehicle Weight

Total weight including driver and fuel

Drivetrain

Affects estimated 0-60 mph time

Engine Horsepower Guide

Three Ways to Measure Engine HP

ET Method: HP = Weight ÷ (ET ÷ 5.825)³ — uses quarter-mile elapsed time
Trap Speed: HP = Weight × (Speed ÷ 234)³ — uses quarter-mile exit speed
Dynamometer: HP = (Torque × RPM) ÷ 5,252 — most accurate method

Safety Warning

Never measure ET or trap speed on public roads — it is illegal and extremely dangerous. Use only on legal drag strips, licensed race tracks, or private property during sanctioned events. Always ensure the vehicle is fully inspected, tires are correctly inflated, and the driver is experienced.

Gross vs Net Horsepower

Gross HP — engine output measured alone on a stand, without accessories. Higher number.
Net HP — measured with accessories (alternator, water pump, power steering). Lower number.

Modern manufacturers advertise net HP. Older (pre-1972) US cars used gross HP, which could be 10-30% higher than net.

Vehicle	HP	Weight (lb)	PTW (hp/lb)	0-60 mph
Toyota Corolla	169	3,100	0.055	~8.0s
Honda Accord	192	3,350	0.057	~7.2s
Ford Mustang GT	450	3,800	0.118	~4.3s
Chevrolet Corvette Z06	650	3,200	0.203	~2.6s
Dodge Challenger SRT Demon	808	4,250	0.190	~2.3s
Lamborghini Huracán	630	3,135	0.201	~2.9s
Tesla Model S Plaid	1,020	4,766	0.214	~1.99s
Bugatti Chiron	1,479	4,398	0.336	~2.4s

Horsepower Types — Key Differences

Mechanical HP: 745.7 W — standard automotive rating
Metric HP (PS/CV): 735.5 W — used in European vehicle specs
Electrical HP: 746 W — exact, used for electric motors
Wheel HP (whp): power measured at driven wheels — 10-20% less than crank HP due to drivetrain losses