Measurement units and drilling formulas

Standard Measurement Units
Quantity/Property Units Multiply By To Obtain Symbol
Depth ft 0.3048 meters m3
Weight on bit (WOB) lbf 0.445 decanewton daN
  4.535 x 10-4 tonne tonne
Nozzle size 32nds in 0.794 millimeters mm
Drill rate ft/hr 0.3048 meters/hour m/hr
Volume barrels 0.1590 cubic meters m3
galUS/stroke 3.785 x 10-3 cubic meters/stroke m3/stroke
Pump output and flow rate galUS/min 3.875 x 10-3 cubic meters/minute m3/min
bbl/stroke an oil barrel is
0.159873 x m3 exactly
cubic meters/stroke m3/stroke
bbl/min 0.1590 cubic meters/minute m3/min
Annular velocity and slip velocity ft/min 0.3048 meters/minute m/min
Linear length and diameter in 25.4 millimeters mm
Pressure psi 6.895 kilopascals kPa
  0.006895 megapascals MPa
  0.06895 bar bar
Mud density lbm/galUS 119.83 kilograms/cubic meter kg/m3
Mud gradient psi/ft 22.621 kilopascals/meter kPa/m
Funnel viscosity s/qt (US) 1.057 seconds/liters s/l
Apparent and plastic viscosity yield point centipoise 1 millipascal seconds mPa.s
Gel strength and stress lbf/100ft2 0.4788 (0.5 for field use) pascals Pa
Cake thickness 32nds in 0.794 millimeters mm
Filter loss mm or cc 1 cubic centimeters cm3
Torque ft.lbf 1.3358 newton meters N.m