Horsepower & Torque Calculator
Quickly convert between horsepower and torque values by entering RPM and one measurement.
Enter the following values to calculate horsepower
Horsepower
What is the Horsepower and Torque Calculator?
This is a specialized digital tool designed to calculate either horsepower or torque, provided you know the other value and your engine’s RPM.
It eliminates manual calculations and applies the universal relationship that binds these three engine parameters together.
This calculator demonstrates the dynamic relationship between power and force at different engine speeds, giving you a practical understanding of how your engine performs across its power band.
Whether you’re verifying dyno results, planning engine upgrades, or simply learning, this tool delivers immediate, accurate conversions.
How to Use the Calculator
- Select Your Calculation: Use the toggle switch to specify whether you want to calculate Horsepower or Torque.
- Enter Your Values:
- To find Horsepower: Input your engine’s known Torque (in lb-ft) and its RPM.
- To find Torque: Input your engine’s known Horsepower and its RPM.
- Calculate.
Parameters
- Horsepower (HP): A measure of the engine’s overall power output, defining how fast work can be done over time. It determines top speed and sustained performance.
- Torque (lb-ft): A measure of the engine’s rotational force or “twisting power.” It’s the immediate force that you feel during acceleration and is crucial for towing and low-end power.
- RPM (Revolutions Per Minute): The speed at which the engine’s crankshaft is spinning. Engine power and torque values are meaningless without specifying the RPM, as they change with engine speed.
- Result Unit: The calculator outputs either HP for horsepower or ft·lbs for pound-feet, ensuring you never confuse the two distinct measurements.
How It Works
The calculator isn’t magic; it’s powered by a fundamental equation in mechanical engineering that defines the relationship between power, torque, and rotational speed.
The core formula is:
HP = (Torque × RPM) / 5252
This equation can be rearranged to solve for any variable:
Where does the constant 5252 come from? It’s a conversion factor that reconciles the different units of measurement. It is derived from the definition of one horsepower (33,000 foot-pounds per minute) and the number of radians in one revolution (2π).
The math works out to 33,000 ÷ (2 × π) ≈ 5,252 . This constant is why on every dyno chart in the world, the torque and horsepower curves always cross at 5,252 RPM.
Horsepower vs. Torque
Many people ask, “Which is more important?” The answer depends entirely on your goals, as they represent different kinds of performance .
| Feature | Torque | Horsepower |
|---|---|---|
| What it is | Instantaneous twisting force | Power output over time |
| Governs | Low-end acceleration, towing ability, hill-climbing | High-speed performance, top speed |
| Analogy | How hard a boxer can punch | How fast a boxer can punch |
| Ideal for | Trucks, heavy-duty vehicles, off-roading | Sports cars, racing, high-revving engines. |
It’s not a choice between one or the other; they are intrinsically linked. Horsepower is essentially torque expressed over time (RPM). You cannot have more horsepower without increasing either torque, RPM, or both.
This is why a large-displacement diesel engine with massive torque but low RPM might have the same horsepower as a small, high-revving gasoline engine with less torque.