# Calculate Specific Gravity (SG) in oilfield unit

This article demonstrates how to calculate Specific Gravity (SG) from different density or pressure gradient  in both oilfield and metric unit.

## 1. Calculate specific gravity using mud weight in PPG

Specific Gravity (SG) = mud weight in ppg ÷ 8.33

Example:
Mud weight = 13.0 ppg
Specific Gravity (SG) = 13.0 ppg ÷ 8.33
Specific Gravity (SG)= 1.56

## 2. Calculate specific gravity using pressure gradient in psi/ft

Specific Gravity (SG) = pressure gradient in psi/ft ÷ 0.433

Example:

Pressure gradient = 0.50 psi/ft
Specific Gravity (SG) = 0.50 psi/ft ÷ 0.433
Specific Gravity (SG) = 1.15

## 3. Calculate specific gravity using mud weight in lb/ft3

Specific Gravity (SG) = mud weight in lb/ft3 ÷ 62.4

Example:

Mud weight = 90 lb/ft3
Specific Gravity (SG)= 90 lb/ft3÷ 62.4
Specific Gravity (SG) = 1.44

## Specific Gravity (SG) = mud weight in kg/m3÷ 1000

Example:
Mud density = 1200 kg/m3
Specific Gravity (SG) = 1200 kg/m3÷ 1000
Specific Gravity (SG)= 1.2

## Specific Gravity (SG) = mud weight in g/cc÷ 1.0

Example:
Mud density = 1.2 g/cc
Specific Gravity (SG) = 1.2 g/cc÷ 1000
Specific Gravity (SG)= 1.2

## Specific Gravity (SG) = pressure gradient in kPa/m ÷ 9.81

Example:
Pressure gradient = 10 kPa/m
Specific Gravity (SG) = 10 kPa/m÷ 9.81
Specific Gravity (SG)= 1.02

Please also find the Excel sheet  for  this topic – Specific Gravity Calculation Sheet 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.

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