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 squareshaped 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 12 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
Frequently Asked Questions (FAQ)FAQ
How do you calculate the acreage of a pond?
To find the acreage of the pond, start by calculating the square footage. For a square or rectangle pond, multiply the length x width in feet. For a round pond, multiply 3.14 x the radius squared. Then, divide your square footage total by 43,560. The result is the acreage of the pond.
How many goldfish can I put in my backyard pond?
As a general rule of thumb, you can add 12 goldfish for every 100 gallons of water. So, if you have a 3,000gallon pond, you can add 3060 goldfish.
How to calculate pond volume in liters?
Calculate pond volume in liters by multiplying the length x width x depth in meters to determine cubic meters. Then multiply the cubic meters by 1,000 to determine liters. Alternatively, if you know your pond volume in US gallons, you can convert it to liters by multiplying it by 3.785412.