This article describes about 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 conversion 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 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.