This post you will learn how to calculate and convert pressure gradient in different units. Please see simple oil field formulas shown each topic below:

**1. Calculate pressure gradient in psi/ft from mud weight in ppg**

Pressure gradient calculation formula:

Pressure gradient in psi/ft = mud weight in ppg x 0.052

Example:

Mud weigt = 9.0 ppg

Pressure gradient in psi/ft = 9.0 x 0.052

Pressure gradient in psi/ft **= **0.468 psi/ft

**2. Calculate ****pressure gradient in psi/ft from mud weight in lb/ft**^{3}

Pressure gradient calculation formula:

Pressure gradient in psi/ft = mud weight in lb/ft^{3} x 0.006944

Example:

Mud weight = 80 lb/ft^{3
}Pressure gradient in psi/ft = 80 lb/ft^{3} x 0.006944

Pressure gradient = 0.55552 psi/ft

OR

Pressure gradient in psi/ft t = mud weight in lb/ft^{3} ÷ 144

Example:

Mud weight = 80 lb/ft^{3
}Pressure gradient in psi/ft = 80 lb/ft^{3} ÷ 144

Pressure gradient = 0.55556 psi/ft

**3. Calculate** **pressure gradient in psi/ft from specific gravity (SG)**

Pressure gradient calculation formula:

Pressure gradient in psi/ft = mud weight in SG x 0.433

Example:

Fluid specific gravity = 2

Pressure gradient in psi/ft = 2.0 x 0.433

Pressure gradient = 0.866 psi/ft

**4. Convert pressure gradient in psi/ft to mud weight in ppg**

Pressure gradient coversion formula:

Mud weight in ppg = pressure gradient in psi/ft ÷ 0.052

Example:

Pressure gradient = 0.5 psi/ft

Mud weight in ppg = 0.5 psi/ft ÷ 0.052

Mud weight = 9.615 ppg

**5. Convert pressure gradient in psi/ft to mud weight in lb/ft**^{3}

Pressure gradient coversion formula:

Mud weight in lb/ft^{3} = pressure gradient in psi/ft ÷ 0.006944

Example:

Pressure gradient = 0.5 psi/ft

Mud weight in lb/ft^{3} = 0.5 psi/ft ÷ 0.006944

Mud weight = 72 lb/ft^{3}

**6. Convert pressure gradient in psi/ft to mud weight in SG**

Pressure gradient coversion formula:

SG = pressure gradient, psi/ft ÷ 0.433

Example: Pressure gradient =0.5 psi/ft

SG = 0.5 psi/ft ÷ 0.433

SG = 1.1547

**Please find the Excel sheet in the following link:** **Pressure Gradient Calculation Sheet**

**Ref book: ** **Formulas and Calculations for Drilling, Production and Workover, Second Edition**