Fresh Water Gradient = .433 psi / ft (9.8 kPa / meter)

API Gravity =  ((141.5 ÷ Specific Gravity) - 131.5)

Specific Gravity =  (141.5 ÷ (API Gravity +131.5))

Torque (ft / lbs) =  ((TNL (meters) x Pump Displacement (M³/day @ 100 RPM) ÷ 125) + Friction Torque)

Polished Rod Speed (RPM) = ((Production Rate (M³/day) x 100) ÷ (Pump Displacement (M³/day @ 100 RPM) x Efficiency))

Nominal Efficiency = observed flow ÷ flow at zero lift     or (D x N - S) ÷ D x N (where E is volumetric efficiency, D is pump displacement, N is speed, and S is Slippage)