Formula & Calculator
Horsepower to Watts Conversion
Converts mechanical power from horsepower to watts, commonly used for motor ratings.
Interpretation
Horsepower to watts conversion: P(W) = HP × 746, because 1 mechanical horsepower is defined as 746 watts.
Example: A 2 HP motor has power P = 2 × 746 = 1492 W.
Variables
| Symbol | Quantity | Unit |
|---|---|---|
| P(W) | Power in watts | W |
| HP | Power in horsepower | hp |
| 746 | Conversion factor (1 hp = 746 W) | dimensionless |
What it means
One mechanical horsepower (HP) is defined as exactly 746 watts. The conversion is P(W) = HP × 746. This is commonly used for motor ratings in the US and other countries. Example: A 2 HP motor has an equivalent electrical power of 2 × 746 = 1492 W. When specifying power supplies or generators, it’s important to account for this value and also consider the motor efficiency and power factor. Understanding this conversion helps in selecting appropriate electrical equipment for motor loads.
Worked example
HP to Watts – Practical Example
Real‑World| Parameter | Value |
|---|---|
| HP | 5 |
| Formula | P(W) = HP × 746 |
Common mistakes
Watch for unit mismatches (W vs kW, single- vs three-phase) and remember to include power factor or efficiency where the formula requires it.Applications
Horsepower to watts conversion: P(W) = HP × 746 is used to convert between mechanical horsepower and electrical watts. Engineers use it to size motors, to compare power ratings, and to perform energy calculations. This conversion is essential for motor and drive selection.
- Motor power rating conversion for electrical design
- Comparison of mechanical and electrical power
- System efficiency and load calculations
- Energy consumption estimation
- Educational understanding of power units
Frequently Asked Questions
P(W) = HP × 746. This is the mechanical horsepower (the most common in the US).
Mechanical HP = 745.7 W; metric HP (PS) = 735.5 W. The 746 W factor is a common approximation for electrical motors.
Motors are often rated in HP (mechanical power), while electrical power is in watts. This conversion is needed for sizing electrical supply.
Common errors: 1) using the wrong conversion factor, 2) using metric HP instead of mechanical, 3) forgetting to include efficiency (for input power), 4) using the factor for small motors incorrectly.
Input power = (HP × 746) / efficiency. For example, a 5 HP motor with 90% efficiency needs 5×746/0.9 = 4144 W.
Sizing electrical circuits for motors, comparing motor efficiencies.
HP = P(W) / 746.
The motor's mechanical output is HP; the electrical input is higher due to losses. The input power is HP×746/η.