Convert Foot-Pound per Second to BTU per Hour (ft·lbf/s → BTU/h)

Converting foot-pounds per second to BTU per hour 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 4.626243

   The conversion factor from ft·lbf/s to BTU/h is 4.626243. Multiply your value by this number.
3. 3
   Read the result in BTU per hour

   The result is your value in BTU per hour (BTU/h).

Multiply the value in foot-pounds per second by 4.626243. For the reverse direction, multiply by 0.216158.

• ✓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 BTU per Hour?

BTU per hour (BTU/h or BTUh) is the standard rating for American heating, air-conditioning, and refrigeration system capacity. A window air conditioner is typically 5,000–12,000 BTU/h, central residential AC ranges 24,000–60,000 BTU/h, and commercial chillers reach 100,000–1,000,000+ BTU/h. The unit's persistence in HVAC reflects American engineering tradition: it directly links cooling/heating capacity to the BTU energy unit familiar in gas-fired equipment. 12,000 BTU/h equals 'one ton of refrigeration' (a unit derived from the heat needed to melt 1 ton of ice in 24 hours), so AC sizes are sometimes given in 'tons' (a 3-ton AC = 36,000 BTU/h). BTU/h relates to the watt (1 W ≈ 3.412 BTU/h), the kilowatt (1 kW ≈ 3,412 BTU/h), and the ton of refrigeration (12,000 BTU/h = 1 ton). Outside the US, kW is dominant for HVAC capacity.

• US air conditioners and heat pumps
• US furnace and boiler ratings
• Some industrial heat-exchanger specs