First, we need to calculate the volume of the water based on the shape of your pond. No worries, if you don’t remember from geometry class in school, we’ll take you through the calculation (math class) here, all you will need are the dimensions of your pond IN FEET and we’ll give you the formula here with the magic conversion number (7.5) to know how many gallons your pond is. If the pond is not exactly rectangular, circular or oval just use average dimensions as close as possible to your pond shape below.
After that you will take the cubic feet number that you have calculated for the volume for your rectangular, circular, or oval shaped pond, and find out how many GALLONS are in the pond. To convert your number in cubic feet to gallons, the magic multiplier number is 7.5. This is because if you have 7.5 gallons in each 1 x 1 x 1 cube of water, thus 7.5 gallons per each cubic foot. So, take your number from above (total in cubic feet) and multiply it by 7.5, and this will give you the total number of gallons of water in your pond!
Rectangular Pond
The easiest shape to figure out would be a rectangular shaped pond: One would multiple the length X width X average depth X 7.5 (magic number) of your pond, and this will give you the total number of gallons of your pond.
Example:
If you have a pond that measures the length is 5 ft. the width is 3 ft. and the depth is 2 ft.
Your calculation would be 5 x 3 x 2 x 7.5 = 225 gallons
Circular Pond
If you have a circle shaped pond, use the diagram of the volume of a cylinder (shown below) to measure the radius and height of your pond. Next use the formula V = Pi x r2 x h. Where r is the radius (The radius is half of the diameter of your pond) and h is the height (or depth) of your pond. Pi is equal to approximately 3.14. You multiply all of these numbers together and it will give you the total volume of your pond. Now that you have the total volume of the pond you multiply this number by 7.5 and it will give you the total number of gallons of your pond.
Example:
If you have a pond where the diameter (or length) is 6ft. The radius is half the diameter, so your radius is 3ft. And the depth (or height) of the pond is 2ft.
pi x radius in ft2 x depth x 7.5 = gallons in your pond
3.14 x 3 x 3 x 2 x 7.5 = 423.9
Oval Pond
If you have an oval shaped pond, use the diagram of an elliptical cylinder (shown below) to measure the length and width of the pond, as well as the height (or depth) of the pond. All measurement should be done in feet. Next use the formula V= Pi x a x b x h. Where “a” is half of the width of your pond, and “b” is half of the length of your pond, and “h” is the height or depth of your pond. This will give you the volume of your pond in cubic feet. You then take the cubic feet and multiply it by 7.5, and this will give you the total number of gallons.
Example:
Pond measurements: width 4′ / length 8′ / depth 2′
pi x ½ width x ½ length x depth x 7.5 = gallons in your pond
3.14 x 2 x 4 x 2 x 7.5 = 376.8