Horsepower and watts are both units of power, but different industries use different standards — and not all horsepower is the same. Enter your Power in Horsepower and select your Horsepower Type (Mechanical, Electrical, Metric, or Boiler) into the Horsepower to Watts Calculator to get the equivalent Power in Watts, along with the exact conversion factor used.
Power in Watts
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The number of watts in a horsepower depends on the type: Mechanical horsepower equals 745.699872 watts, electrical horsepower equals 746 watts, metric horsepower equals 735.49875 watts, and boiler horsepower equals 9809.5 watts.
Mechanical horsepower (745.7 watts) is the original definition based on James Watt's comparison to draft horses. Electrical horsepower (746 watts) is used for rating electric motors and is slightly higher than mechanical horsepower.
Metric horsepower is a European standard equal to 735.49875 watts or 75 kilogram-force meters per second. It's commonly used in automotive applications outside of the United States.
To convert horsepower to watts, multiply the horsepower value by the appropriate conversion factor: 745.699872 for mechanical HP, 746 for electrical HP, 735.49875 for metric HP, or 9809.5 for boiler HP.
Boiler horsepower is used to rate steam boilers and equals 9809.5 watts. It represents the ability to evaporate 34.5 pounds of water per hour at 212°F (100°C) from and at 212°F.
Different types of horsepower evolved for different applications and regions. Mechanical HP is the original standard, electrical HP is for motors, metric HP is used in Europe and automotive, and boiler HP is specific to steam applications.
A watt is the SI unit of power, equal to one joule per second. It measures the rate of energy transfer and is named after James Watt, the same person who popularized the horsepower unit.