Torque to HP Calculator

Automotive Engineering & Dynamometer Power Physics

Horsepower and torque are mathematically coupled by rotational angular velocity.

Primary Powertrain Equations

• Imperial Horsepower Formula:

HP = Torque (lb-ft) × RPM5,252.11

• Metric Power in Kilowatts:

kW = Torque (N·m) × RPM9,549

• Metric Horsepower: PS = HP × 1.01387

• Wheel Horsepower (WHP): WHP = HP × (1 - Drivetrain Loss \%100)

Why Do Horsepower and Torque Curves Always Cross at 5,252 RPM?

By definition, 1 HP = 33,000 ft-lbs per minute. Converting rotational RPM to linear velocity requires multiplying by 2π. Therefore: (33,000) / (2π) = 5,252.

• Whenever RPM = 5,252, HP = Torque (in lb-ft).

How to Use This Calculator

Enter your Torque Output (e.g. 350), Torque Unit — choose from Pound-Feet (lb-ft — Imperial Standard), Newton-Meters (N·m — Metric Standard), Inch-Pounds (in-lb), Engine Speed (RPM) (e.g. 5500 in RPM), and Drivetrain Parasitic Loss (%) (e.g. 15 in %). Results update instantly as you type — adjust any value to compare scenarios.

The Formula

HP = (Torque * RPM) / 5252.113

Worked Example

A V8 engine delivering 350 lb-ft of torque at 5,500 RPM produces 366.52 crank horsepower (311.54 WHP at the wheels after standard 15% transmission loss).

Understanding Your Result

Unit conversion precision: round to the same number of significant figures as your original measurement. Converting 6 feet to meters gives 1.8288 m — but if your measurement was approximate (±1 inch), expressing more than 2 decimal places is false precision. For international trade and technical specifications, SI units (meters, kilograms, liters) are the standard. US customary units (feet, pounds, gallons) differ from Imperial UK units: 1 US gallon = 3.785 L vs. 1 UK gallon = 4.546 L.