Unit Conversion

Torque & Power Converter

Convert between HP, kW, Nm, and lb-ft across different RPMs.

Input Parameters

Convert

Torque

Input Unit

Rotational Speed

RPM

Output Unit

Results

Enter values and click Convert

What is Torque-Power Conversion?

Torque and power are related by rotational speed. Given any two of these values, you can calculate the third. This converter handles conversions between various torque and power units.

This relationship is fundamental for motor selection, gearbox design, and understanding mechanical systems.

How to Use

Select conversion direction (Torque→Power or Power→Torque)
Enter your known value and select its unit
Enter the rotational speed in RPM
Select your desired output unit
Click Convert to see all equivalent values

FAQs

Power = Torque × Angular Velocity. At constant power, torque and speed are inversely related. This is why gearboxes trade speed for torque. The formula HP = (lb-ft × RPM) ÷ 5252 directly shows this relationship.

The constant 5252 converts units: 1 HP = 33,000 lb-ft/min of work. Dividing by 2π (radians per revolution) and simplifying: 33,000 ÷ (2 × 3.14159) ≈ 5252. This makes the formula work with RPM instead of radians/min.

It depends on the application. Torque determines acceleration and ability to do work at low speed (pulling loads, climbing hills). Horsepower determines top speed and sustained work rate. For most machinery, you need to match both to the application.

Key conversions: 1 HP = 0.7457 kW, 1 lb-ft = 1.3558 N-m, 1 lb-ft = 12 lb-in. For metric power: kW = (N-m × RPM) ÷ 9549. This calculator does all conversions automatically.

Brake HP (BHP) is measured at the output shaft and accounts for internal losses. Indicated HP is theoretical power from combustion. For electric motors, nameplate HP is output power. Always clarify which is being specified.

Limitations

• Assumes steady-state conditions (constant speed)
• Does not account for efficiency losses in drive systems
• Imperial HP used (metric HP is slightly different)
• Torque curves vary with speed for real motors
• Starting torque differs from running torque