Borehole Grout Volume Calculator – Calculate Grouting Requirements with Ease

Last updated: 21 May 2025 | Author: Brij | Review By: Irshad

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Calculate the required borehole grout volume in cubic feet, meters, gallons, or liters. Enter borehole diameter, casing size, depth, and shrinkage factor.

Borehole Diameter:

Borehole Depth:

Casing Outer Diameter (Optional):

Grout Shrinkage (%):

Output Volume Unit:

Grout Volume Results

Annular Volume:

ft³

Grout Volume Required:

ft³

Liquid Volume Equivalent:

gal

Grouting is a crucial part of borehole construction to seal the annular space between the borehole wall and casing. Use our Borehole Grout Volume Calculator to estimate how much grout is needed to properly fill that space, accounting for borehole diameter, casing outer diameter, depth, and shrinkage.

What Is Borehole Grouting?

Borehole grouting is the process of filling the annular space (the space between the borehole wall and casing or between two concentric pipes) with a sealing material—usually bentonite, cement, or a sand mix. This is crucial to prevent groundwater contamination and provide structural support.

Borehole Grout Volume Formula

To find the grout volume needed to fill the space between the borehole and casing, follow these steps:

Step 1: Annular Area (in square inches)

$A = \frac{\pi}{4} \times (D_{\text{bore}}^2 - D_{\text{casing}}^2)$

Step 2: Annular Volume (in cubic inches)

$V_{\text{in³}} = A \times H$

Where:

$A$ = annular area (from Step 1)
$H$ = depth in inches (1 foot = 12 inches)

Step 3: Convert to Cubic Feet

$V_{\text{ft³}} = \frac{V_{\text{in³}}}{1728}$

Step 4: Apply Shrinkage Factor

$V_{\text{grout}} = V_{\text{ft³}} \times \left(1 + \frac{\text{shrinkage\%}}{100}\right)$

Step 5: Convert to Gallons or Liters (Optional)

Gallons:

$V_{\text{gal}} = V_{\text{ft³}} \times 7.48052$

Liters:

$V_{\text{L}} = V_{\text{ft³}} \times 28.3168$

Example Calculation

Given:

Borehole Diameter = 6 inches
Casing Outer Diameter = 4 inches
Borehole Depth = 50 feet
Shrinkage Factor = 5%

Step 1: Annular Area

$A = \frac{\pi}{4} \times (6^2 - 4^2) = \frac{3.1416}{4} \times (36 - 16) = 15.708 \text{ in²}$

Step 2: Volume in Cubic Inches

$V_{\text{in³}} = 15.708 \times (50 \times 12) = 15.708 \times 600 = 9,424.8 \text{ in³}$

Step 3: Convert to Cubic Feet

$V_{\text{ft³}} = \frac{9424.8}{1728} = 5.454 \text{ ft³}$

Step 4: Add Shrinkage (5%)

$V_{\text{grout}} = 5.454 \times \left(1 + \frac{5}{100}\right) = 5.454 \times 1.05 = 5.726 \text{ ft³}$

Step 5: Convert to Gallons and Liters

Gallons:

$V_{\text{gal}} = 5.726 \times 7.48052 = 42.83 \text{ gallons}$

Liters:

$V_{\text{L}} = 5.726 \times 28.3168 = 162.19 \text{ liters}$

Final Answer:

Grout Volume (ft³) = 5.726 ft³
Grout Volume (gallons) = 42.83 gal
Grout Volume (liters) = 162.19 L

Frequently Asked Questions (FAQs)

1. Why is shrinkage factor important when calculating grout volume?

Answer: Grout materials tend to shrink slightly as they cure and settle. To ensure the annular space is completely filled and sealed, it's important to add a shrinkage factor—commonly around 5%—to compensate for this reduction in volume after application.

2. What units should I use when inputting measurements?

Answer: Use inches for borehole and casing diameters, and feet for borehole depth. The calculator will handle conversions internally and provide results in cubic feet, gallons, and liters for your convenience.

3. Can I use this calculator for both water wells and geothermal boreholes?

Answer: Yes! This calculator works for any type of borehole where grouting is required between the casing and borehole wall, including water wells, geothermal wells, and monitoring wells, as long as accurate input dimensions are provided.

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