Convert Foot-Pound per Second to Mechanical Horsepower (ft·lbf/s → hp)

Converting foot-pounds per second to mechanical horsepower is straightforward: multiply by the conversion factor. Follow these three steps to do it by hand or in your head.

1. 1
   Take your value in foot-pounds per second

   Start with the number of foot-pounds per second (ft·lbf/s) you want to convert.
2. 2
   Multiply by 0.001818

   The conversion factor from ft·lbf/s to hp is 0.001818. Multiply your value by this number.
3. 3
   Read the result in mechanical horsepower

   The result is your value in mechanical horsepower (hp).

Multiply the value in foot-pounds per second by 0.001818. For the reverse direction, multiply by 550.

• ✓1 ft·lbf/s = 1.356 W.
• ✓550 ft·lbf/s = 1 mechanical hp.
• ✓Rarely needed today outside archival references.

• ✗Confusing ft·lbf/s (power) with ft·lbf (torque or work).
• ✗Using in modern specifications — prefer W or kW.
• ✗Mixing with foot-pound (energy) in same calculation.

What is the Foot-Pound per Second?

The foot-pound per second (ft·lb/s) is the American mechanical-power unit, used in engineering and machine-rating contexts. James Watt's original definition of 1 horsepower was 33,000 ft·lb/min = 550 ft·lb/s, so the foot-pound per second is the granular American power unit underlying horsepower calculations. It is rare in everyday use (kW or hp dominate American power specifications) but appears in engineering thermodynamics textbooks, mechanical-design calculations, and ballistics-energy contexts. The ft·lb/s relates to the watt (1 ft·lb/s ≈ 1.356 W), horsepower (550 ft·lb/s = 1 hp), and the BTU per hour (1 ft·lb/s ≈ 4.626 BTU/h). It is part of the legacy US customary unit system that retains a foothold in mechanical engineering despite metric advancement.

• Older US mechanical-engineering calculations
• Some US physics textbooks
• Classical-mechanics problems

What is the Mechanical Horsepower?

Horsepower (hp) equals exactly 745.6998715822702 watts (mechanical horsepower) and is the American and British unit for car engines, motorcycles, motorboats, and traditional mechanical power ratings. James Watt invented the unit in the 1780s to market his steam engines: he calculated that a brewery horse could continuously turn a mill wheel at 33,000 ft·lb per minute, which became 1 horsepower. American cars typically range from 150 hp (economy) to 700 hp (sports cars), pickup trucks 250–500 hp, and large diesel trucks 400–600 hp. Outside the US, the metric horsepower (PS or CV, equal to 735.5 W — about 1.4% smaller than mechanical hp) is sometimes used. Horsepower relates to the watt (1 hp ≈ 745.7 W), the kilowatt (1 hp ≈ 0.746 kW), and the metric horsepower (1 hp ≈ 1.014 PS). Despite SI's preference for the watt, horsepower remains entrenched in automotive marketing.

• US car and motorcycle engine ratings
• Lawn mower and small engine specs
• US pump and compressor ratings