Question 1

How do you calculate horsepower from torque?

Accepted Answer

The formula to calculate Mechanical Horsepower is: HP = (Torque × RPM) / 5252. The Torque must be measured in pound-feet (lb-ft) and engine speed in Revolutions Per Minute (RPM).

Question 2

Why do torque and horsepower always cross at 5,252 RPM?

Accepted Answer

This is a mathematical constant rooted in how a horsepower is defined (33,000 foot-pounds of work per minute) and the geometry of a circle (2π radians). When you multiply Torque (in lb-ft) by 5,252 and divide by 5,252, the resulting Horsepower is exactly equal to the Torque.

Question 3

What is the difference between HP, kW, and PS?

Accepted Answer

Mechanical Horsepower (HP or bhp) is the imperial standard. Kilowatt (kW) is the metric standard for power output, often used for electric vehicles. PS (Pferdestärke) is the metric horsepower standard heavily used in Germany and Japan. 1 HP = 0.7457 kW = 1.01387 PS.

Question 4

How do I convert Newton-Meters (Nm) to Horsepower?

Accepted Answer

First, you must convert the Newton-Meters to pound-feet by multiplying by 0.73756. Once you have the torque in lb-ft, you can apply the standard formula: (Torque lb-ft × RPM) / 5252. Our calculator does this conversion automatically.

Question 5

What is the difference between Brake Horsepower (bhp) and wheel horsepower (whp)?

Accepted Answer

Brake Horsepower (bhp) is the power measured directly at the engine's crankshaft, without the drivetrain connected. Wheel horsepower (whp) is what actually makes it to the tires after transmission and drivetrain losses (usually 15-20% less than bhp).

Engine Horsepower Calculator

The 5252 Rule

Torque vs. Horsepower

What is Torque?

What is Horsepower?

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