Calculator: How Much Pond Liner You Need

Our pond calculator will compute the volume of your pond, the square footage, and the estimated pond liner size. We’ve also provided manual pond volume calculations you can use on the go.

Pond Calculator – Finding Square Footage and Pond Volume

Enter the length, width, and depth of your pond in feet. Our calculator will automatically display the square footage and pond volume in US gallons.

The formula to determine the square footage of  a rectangular or square pond is:

Square footage = length (ft) x width (ft)

If your pond is circular, use the following square footage formula:

Square footage = 3.14 x radius (ft) x radius (ft)

The formula to determine the number of gallons your rectangle or square-shaped pond will hold is:

Pond volume = length (ft) x width (ft) x depth (ft) x 7.5

If your pond is circular, you’ll need to use a different equation for pond volume:

Circular pond volume = 3.14 x radius (ft) x radius (ft) x depth (ft) x 7.5

Pond Calculator – Determining Liner Size

Most pond liners come in rectangular sheets, so you’ll need to calculate the liner length and width, plus account for an overhang. The recommended pond liner overhang is 1-2 feet.

Pond liner length = length + (depth x 2) + overlap

Pond liner width = width + (depth X 2) + overlap

For a circular pond, use the following pool liner formula:

Pool liner = diameter + 2 * (depth + overlap)

Calculating the Square Footage, Volume, and Liner Length of a Pond: Example for a Rectangular Pond

In our example, we’ll calculate pond measurements for a 10′ x 15′ x 3′ backyard pond. To calculate the square footage, we’ll multiply the length by the width, which is 10 x 15, for a total of 150 square feet. 

To determine the number of US gallons our pond will hold, we’ll first find the cubic feet by multiplying the length x width x depth in feet.

• Cubic feet = 10 x 15 x 3
• Cubic feet= 450
• Since there are about 7.5 gallons in one cubic foot, we’ll multiply by 7.5
• 450 x 7.5 = 3,375 US gallons

Now that we know how much water our pond can hold, let’s figure out what size liner we need. To find liner size, we must make two calculations – one for the length and one for the width. We also need to account for overlap. Since recommended overlap is 1 to 2 feet, we’ll place a “2” in the overlap portion of our equation.

• • Pond liner length = length + (depth x 2) + overlap
  • Pond liner length = 10’ + (3’ x 2) + 2

• Pond liner length = 18 ft

• • Pond liner width = width + (depth x 2) + overlap
  • Pond liner width = 15’ + (3’ x 2) + 2

Most pond liners come in 5’ multiples, so we’d need to purchase a 20’ x 25’ pond liner.

Pond Liner, Gallons, and Square Footage Calculation Examples of a Circular Pond

In our example, we’ll perform calculations for a 24’ round pond with a 3’ depth. 

First, to determine square footage, we’ll fill in the following formula:

• • Square footage = 3.14 x radius (ft) x radius (ft)
  • The diameter of our pond is 24, making the radius 12 ft (half the diameter)
  • Square footage = 3.14 x 12’ x 12’

To figure out how many gallons of water our round pond will hold, we’ll use the following equation:

• • Circular pond volume = 3.14 x radius (ft) x radius (ft) x depth (ft) x 7.5
  • Circular pond volume = 3.14 x 12’ x 12’ x 3’ x 7.5

• Circular pond volume = 10,174 gallons of water

To determine the size of the pond liner to purchase, we’ll use the following equations and 2 feet as our overlap value:

• • Pool liner = diameter + 2 * (depth + overlap)
  • Pool liner = 24’ + 2 * (3’ + 2)

• Pool liner = 34’ round pond liner