This article presents the main conversion factors for oil field and SI units.
Length/Depth/Distance (SI unit - m)
1 inch (") = 25.4 mm
1 foot (ft) = 0.3048 m (= 12 inches)
1 nautical mile = 1852 m (= 6080 feet)
Velocity (SI unit - m/s)
1 knot = 1.852 km/h (1 knot = 1 nautical mile per hour)
1 mile/hour = 1.6093 km/h = 0.4470 m/s
1 ft/sec = 1.0973 km/h = 0.3048 m/s
1 km/hour = 0.2778 m/s
Area (SI unit - m2)
1 inch2 = 6.4516 cm2
1 ft2 = 0.0929 m2
Volume (SI unit - m3)
1 gallon (US) = 3.7854 litres
1 ft3 = 0.0283 m3
1 std.cu.ft of gas = 0.02826 m3 (at 15oC and 101.325 Pa)
1 barrel (bbl) = 0.15898 m3 (1 barrel = 42 US gal)
Flow (SI unit - m3/s)
1 gal US/min = 5.4509 m3/d =0.2271 m3/hr
103 st. cuft/day = 28.2625 m3/d =1.1776 m3/hr
103 bbl/day = 158.9873 m3/d =6.6244 m3/hr
Mass (SI unit - kg)
1 pound = 0.45359 kg
1 short ton = 907.185 kg (= 2000 lbs)
1 long ton = 1016.05 kg (= 2240 lbs)
1 tonne (MT) = 1000.00 kg
Pressure and Stress (SI unit - Pa)
1 psi = 6.8948 kPa
1 kgf/cm2 = 98.0665 kPa
1 st. atmosphere = 101.325 kPa
1 bar = 100.00 kPa =14.50 psi
Power (SI unit - W)
1 Hp = 745.699 W
Density (Mass/Unit Length) (SI unit - kg/m)
1 lb/ft = 1.4882 kg/m
Density (Mass/Unit Volume) (SI unit - kg/m3)
1 lb/ft3 = 16.0185 kg/m3
1 lb/gal US = 119.826 kg/m3
1 lb/barrel US = 2.853 kg/m3
Viscosity (Kinematic) (SI unit - m2/s)
1 cSt (centistoke) = 1 mm2/s
Viscosity (Dynamic) (SI unit - Pa.s)
1 cP (centipoise) = 1 mPa.s
Temperature (SI unit K)
Temp oF = 9/5 (Temp oC) + 32
Temp oC = 5/9 (Temp oF - 32)
Torque (SI unit -Nm)
1 ft.lb = 0.1383 kgm = 1.356 Nm
Pressure Gradient (SI unit - Pa/m)
1 kPa/m = 0.01 bar/m = 0.0442 psi/ft
Density / Pressure Gradient Conversion (Based on the P= g h formula)
1 bar/m = 8.51 lb/gal (US) = 1.02 kg/dm3 (kg/litre)