How it works
Determine an engine’s mechanical horsepower by providing its torque output and rotational speed (RPM).
Input query strings and outputs
Use an input name in this page’s URL as ?name=value, and join additional inputs with &. Portable shared links may instead use the compact ?ac= state parameter.
Input query strings
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?torque=Torque (lb-ft)Number · Optional · Default: 300
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?rpm=Rotational Speed (RPM)Number · Optional · Default: 5,252
Outputs
1-
resultResultText · Primary output
result contains the calculator’s complete rendered result area, including its visible result cards, tables, charts, and messages.
Calculate engine horsepower from torque and measurement speed (RPM)
Description
The Horsepower Calculator is a fundamental automotive tool used to determine the power output of an engine. In physics, horsepower is the speed at which work is done. By measuring the twisting force (Torque) an engine produces and the speed at which it is spinning (RPM), this tool calculates the total horsepower. This is essential for comparing engine performance and understanding vehicle dynamics.
Inputs
- Torque (lb-ft): The rotational force generated by the engine.
- Engine Speed (RPM): The number of revolutions per minute the engine is spinning.
Outputs
- Horsepower: The calculated power output in HP.
Chart
- N/A: This tool provides a direct numeric mechanical result.
“Good to Know”
- The Magic Number: Horsepower and Torque always cross at 5,252 RPM. This is because of the mathematical constant used in the formula.
- The Formula: $\text{HP} = (\text{Torque} \times \text{RPM}) \div 5252$.
- Torque vs. Horsepower: Torque represents the “grunt” or “pulling power” (low-end acceleration), while horsepower represents the “work rate” or “top speed” (high-end power).
Examples
Example 1: High Torque Truck
- Input: 450 lb-ft, 2500 RPM
- Output: 214.2 HP
Example 2: Revv-Happy Sports Car
- Input: 200 lb-ft, 8000 RPM
- Output: 304.6 HP
Example 3: Equilibrium Point
- Input: 300 lb-ft, 5252 RPM
- Output: 300.0 HP