How many watts equals one horsepower?

• A. 700
• B. 746
• C. 740
• D. 800

Answer: (C)

Power is measured in watts, and horsepower is a traditional unit used for engines. By definition, one horsepower equals 550 foot-pounds of work per second. To convert to watts, use that 1 foot-pound is 1.355818 joules, so 550 × 1.355818 ≈ 745.7 joules per second, i.e., 745.7 watts. In practice this is commonly rounded to 746 watts. There’s also a metric horsepower definition (about 735.5 watts), but for the standard horsepower often used in HVAC and mechanical contexts, 746 watts per horsepower is the typical figure.