HP → Watts
- Created by
- Renato Passos, Eng. de Software
- Reviewed by
- Renato Passos, Eng. de Software
Last updated: Apr 18, 2026
About this calculator
The HP → Watts calculator converts mechanical power in horsepower (HP) to watts (W) using the standard formula 1 HP = 745.7 W. This conversion is widely applied in engineering and physics to determine the work capacity of motors, pumps, and industrial equipment. The formula derives from the equivalence between mechanical and electrical energy, rooted in thermodynamics.
It is useful for applications like motor sizing, energy efficiency analysis, or comparing equipment performance. For example, a 5 HP motor would have 3,728.5 W of power. It's crucial to verify whether the HP value follows the imperial standard (common in the US) or the metric standard (used in Europe), as conversion factors may vary slightly.
Caveats: This calculator assumes the imperial HP standard (745.7 W). If the HP is metric (1 metric HP ≈ 735.5 W), the result will be inaccurate. Always confirm the equipment's technical specification and avoid using approximate values in critical calculations. When in doubt, consult the manufacturer's manual or a qualified professional.
Frequently asked questions
Why use 745.7 W for 1 HP?
The 745.7 W value represents the imperial horsepower standard, adopted in the US and globally. It's based on James Watt's calculations to compare steam engine power with animal labor.
How does metric vs imperial HP differ?
Metric HP (≈735.5 W) is used in Europe. The difference arises because imperial HP uses 550 foot-pounds per second, while metric HP uses 75 kgf·m/s. This converter defaults to imperial HP.
Can I use this for electrical equipment?
Yes, as long as the HP value refers to the mechanical power generated by the electrical equipment. Motors often list their power in HP or W, so the conversion applies.
What if I enter a negative value?
The calculator ignores negative values since power can't be negative in physical/engineering contexts. A warning will ask for a positive number above zero.