Power Conversion Factor
Beginning with the definitions of the derived units (ft.lb)/s and W in the USCS and SI, verify the conversion factors between them in Table 7.2.
Table 7.2 Conversion Factors Between Various Units for Power in the USCS and SI
| (ft . lb)/s | W | hp |
| 1 | 1.356 | 1.818×10^{-3} |
| 0.7376 | 1 | 1.341×10^{-3} |
| 550 | 745.7 | 1 |
Approach
The watt is defined by work being performed at the rate of one joule per second. To relate the two units for power, we must convert the dimensions for force and length appearing in the definition of the joule (1 J = 1 N . m).
Referring to Table 3.6, 1 ft = 0.3048 m and 1 lb = 4.448 N.
Table 3.6 Conversion Factors between Certain Quantities in the USCS and SI
| Quantity | Conversion |
| Length | 1 in. = 25.4 mm |
| 1 in. = 0.0254 m | |
| 1 ft = 0.3048 m | |
| 1 mi = 1.609 km | |
| 1 mm = 3.9370 ×10^{-2} in. | |
| 1 m = 39.37 in. | |
| 1 m = 3.2808 ft | |
| 1 km = 0.6214 mi | |
| Area | 1 in^2 = 645.16 mm^2 |
| 1 ft^2 = 9.2903 × 10^{-2} m^2 | |
| 1 mm^2 = 1.5500 × 10^{-3 }in^2 | |
| 1 m^2 = 10.7639 ft^2 | |
| Volume | 1 ft^3 = 2.832 × 10^{-2} m^3 |
| 1 ft^3 = 28.32 L | |
| 1 gal = 3.7854 × 10^{-3} m^3 | |
| 1 gal = 3.7854 L | |
| 1 m^3 = 35.32 ft^3 | |
| 1 L = 3.532 × 10^{-2} ft^3 | |
| 1 m^3 = 264.2 gal | |
| 1 L = 0.2642 gal | |
| Mass | 1 slug = 14.5939 kg |
| 1 lbm = 0.45359 kg | |
| 1 kg = 6.8522 × 10^{-2} slugs | |
| 1 kg = 2.2046 lbm | |
| Force | 1 lb = 4.4482 N |
| 1 N = 0.22481 lb | |
| Pressure or stress | 1 psi = 6895 Pa |
| 1 psi = 6.895 kPa | |
| 1 Pa = 1.450 × 10^{-4 }psi | |
| 1 kPa = 0.1450 psi | |
| Work, energy, or heat | 1 ft · lb = 1.356 J |
| 1 Btu = 1055 J | |
| 1 J = 0.7376 ft · lb | |
| 1 J = 9.478 × 10^{-4} Btu | |
| Power | 1 (ft · lb)/s = 1.356 W |
| 1 hp = 0.7457 kW | |
| 1 W = 0.7376 (ft · lb)/s | |
| 1 kW = 1.341 hp |
