## Conversion Tables, Constants, and Material Properties

General conversion factors (to five significant digits)
QuantityU.S. unitSI equivalent
Length1 in0.025400 m
1 ft0.30480 m
1 mile1609.3 m
Area1 in20.64516 × 10−3 m2
1 ft20.092903 m2
1 acre4046.9 m2
Volume1 in30.016387 × 10−3 m3
1 ft30.028317 m3
1 US gallon3.7854 × 10−3 m3

Conversion factors for stress analysis
QuantityU.S. unitSI equivalent
Density1 slug/ft3 = 1 lbf s2/ft4515.38 kg/m3
1 lbf s2/in410.687 × 106 kg/m3
Energy1 ft lbf1.3558 J (N m)
Force1 lbf4.4482 N (kg m/s2)
Mass1 slug = 1 lbf s2/ft14.594 kg (N s2/m)
1 lbf s2/in175.13 kg
Power1 ft lbf/s1.3558 W (N m/s)
Pressure, Stress1 psi (lbf/in2)6894.8 Pa (N/m2)

Conversion factors for heat transfer analysis
QuantityU.S. unitSI equivalent
Conductivity1 Btu/ft hr °F1.7307 W/m °C
1 Btu/in hr °F20.769 W/m °C
Density1 lbm/in327680. kg/m3
Energy1 Btu1055.1 J
Heat flux density1 Btu/in2 hr454.26 W/m2
Power1 Btu/hr0.29307 W
Specific heat1 Btu/lbm °F4186.8 J/kg °C
Temperature1 °F5/9 °C
Temp °F9/5 × Temp °C + 32°
9/5 × Temp °K − 459.67°

Important constants
ConstantU.S. unitSI unit
Absolute zero−459.67 °F−273.15 °C
Acceleration of gravity32.174 ft/s29.8066 m/s2
Atmospheric pressure14.694 psi0.10132 × 106 Pa
Stefan-Boltzmann constant0.1714 × 10−8 Btu/hr ft2 °R45.669 × 10−8 W/m2 °K4
where °R = °F + 459.67where °K = °C + 273.15

Approximate properties of mild steel at room temperature
QuantityU.S. unitSI unit
Conductivity28.9 Btu/ft hr °F50 W/m °C
2.4 Btu/in hr °F
Density15.13 slug/ft3 (lbf s2/ft4)7800 kg/m3
0.730 × 10−3 lbf s2/in4
0.282 lbm/in3
Elastic modulus30 × 106 psi207 × 109 Pa
Specific heat0.11 Btu/lbm °F460 J/kg °C
Yield stress30 × 103 psi207 × 106 Pa