Engine Horsepower Calculator

Calculate engine horsepower from torque and RPM, calculate torque from horsepower and RPM, or calculate RPM from horsepower and torque with step-by-step solutions.

Input

Calculate Engine Horsepower

Select a calculation type and enter values to see results with detailed step-by-step solutions.

Complete User Guide

What is Engine Horsepower?

Horsepower (HP) is a unit of measurement for engine power output. It represents the rate at which work is done. In automotive applications, horsepower is calculated from torque and RPM using the formula: HP = (Torque × RPM) / 5252. This calculator helps you determine horsepower, torque, or RPM when you know two of these three values.

How to Use This Calculator

  1. Select a calculation type from the dropdown (Calculate Horsepower, Calculate Torque, Calculate RPM, Convert Power Units, or Convert Torque Units).
  2. Enter the required values in the input form.
  3. Select appropriate units for your inputs and desired result.
  4. Click 'Calculate' to see the results.
  5. Review the detailed results, visualizations, and step-by-step solution.

Calculation Types

Calculate Horsepower

Enter torque and RPM to calculate horsepower. Formula: HP = (Torque × RPM) / 5252. This is the most common calculation for determining engine power.

Calculate Torque

Enter horsepower and RPM to calculate torque. Formula: Torque = (HP × 5252) / RPM. Torque measures the rotational force of the engine.

Calculate RPM

Enter horsepower and torque to calculate RPM. Formula: RPM = (HP × 5252) / Torque. Useful for finding the engine speed at peak power.

Convert Power Units

Convert between different power units: HP (horsepower), kW (kilowatts), PS (metric horsepower), and BHP (brake horsepower).

Horsepower Formula

Horsepower Formula:

HP = (Torque × RPM) / 5252

Where:

  • HP = Horsepower
  • Torque = Torque (lb⋅ft)
  • RPM = Revolutions Per Minute
  • 5252 = Constant derived from unit conversions

The constant 5252 comes from the conversion between foot-pounds per minute and horsepower. At 5252 RPM, torque and horsepower are numerically equal. This formula is the standard method for calculating engine horsepower in the automotive industry.

Supported Units

Power Units

  • HP (Horsepower - US standard)
  • kW (Kilowatts - SI unit)
  • PS (Pferdestärke - Metric horsepower)
  • BHP (Brake Horsepower - Same as HP)

Torque Units

  • lb⋅ft (Pound-feet - US standard)
  • N⋅m (Newton-meters - SI unit)
  • kg⋅m (Kilogram-meters - Metric unit)

Typical Engine Values

Vehicle Type Typical HP Typical Torque (lb⋅ft) Peak RPM
Economy Car100-150100-1504000-6000
Sports Car300-500250-4006000-8000
Truck/SUV200-400300-5003000-5000
Supercar500-1000+400-7007000-9000

Important Notes

  • All input values must be positive numbers (non-negative).
  • RPM must be greater than zero when used as a divisor in torque calculations.
  • Torque must be greater than zero when used as a divisor in RPM calculations.
  • The constant 5252 is specific to lb⋅ft and HP units. For metric units, conversions are applied first.
  • Horsepower and torque are related but measure different aspects of engine performance.
  • Peak horsepower and peak torque typically occur at different RPM values.
  • The calculator automatically handles unit conversions between different measurement systems.
  • Results are displayed with step-by-step solutions showing the calculation process.

Common Applications

  • Automotive performance analysis and tuning
  • Engine dyno testing and verification
  • Comparing engine specifications
  • Educational purposes for automotive engineering students
  • Racing and performance optimization
  • Vehicle modification planning
  • Understanding engine power curves

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