Referring to the previous article, Calculate Specific Gravity (SG) in oilfield unit , you get specific gravity (SG) from mud weight (ppg and lb/ft3) and pressure gradient (psi/ft) but you may need to reverse calculation from specific gravity (SG) to mud weight or pressure gradient (psi/ft). In this article, you will learn how to convert specific gravity to mud weight and pressure gradient in both oilfield and metric unit by using simple formulas as follows:
Convert Specific Gravity to Mud Weight In Oilfield Unit
Convert specific gravity to mud weight in pounds per gallon (ppg)
Mud weight in ppg = specific gravity (SG) × 8.33
Example: specific gravity = 1.50
mud wt, ppg = 1.50 × 8.33
mud wt = 12.5 ppg
Convert specific gravity to mud weight in lb/ft3
Mud weight in lb/ft3 = specific gravity × 62.4
Example: specific gravity = 1.50
Mud weight in lb/ft3 = 1.50 × 62.4 lb/ft3
Mud weight in lb/ft3 = 93.6 lb/ft3
Convert specific gravity to pressure gradient in psi/ft
Pressure gradient in psi/ft = specific gravity (SG) × 0.433
Example: specific gravity = 1.5
Pressure gradient in psi/ft = 1.5 × 0.433
Pressure gradient in psi/ft = 0.650 psi/ft
Convert Specific Gravity to Mud Weight In Metric Unit
Convert specific gravity to mud weight in kg/m3
Mud weight in kg/m3 = specific gravity × 1000
Example: specific gravity = 1.5
Mud weight in kg/m3 = 1.5 × 1,000
Mud weight in kg/m3 = 1,500
Convert specific gravity to mud weight in g/cc
Mud weight in g/cc = specific gravity × 1.0
Example: specific gravity = 1.5
Mud weight in g/cc = 1.5 × 1.0
Mud weight in g/cc = 1.5
Convert specific gravity to pressure gradient in kPa/m
Pressure gradient in kPa/m = specific gravity (SG) × 9.81
Example: specific gravity = 1.5
Pressure gradient in kPa/m = 1.5 × 9.81
Pressure gradient in kPa/m = 14.7
Please also find the Excel sheet for this topic. 
Ref books:
Lapeyrouse, N.J., 2002. Formulas and calculations for drilling, production and workover, Boston: Gulf Professional publishing.
Bourgoyne, A.J.T., Chenevert , M.E. & Millheim, K.K., 1986. SPE Textbook Series, Volume 2: Applied Drilling Engineering, Society of Petroleum Engineers.
Mitchell, R.F., Miska, S. & Aadny, B.S., 2011. Fundamentals of drilling engineering, Richardson, TX: Society of Petroleum Engineers.
