Enter the shape, size and average depth of your pond to see how many gallons it holds and what size pump will circulate it.
How to use the pond volume calculator
- Pick the shape closest to your pond. Use irregular for kidney and freeform ponds.
- Enter the length and width at the water surface. For a round pond enter the diameter as the length.
- Enter the average depth of the water, not the depth of the hole. If the pond has shelves, estimate the average across the whole surface.
Formulas
Rectangle: area = length × width Round: area = π × (diameter ÷ 2)² Oval: area = π ÷ 4 × length × width Irregular: area ≈ length × width × 0.85 Volume (ft³) = area × average depth Gallons = cubic feet × 7.48 Liters = gallons × 3.785
The irregular figure is an approximation: a freeform pond usually fills about 85% of the rectangle drawn around it. For an exact number, time how long a hose takes to fill a 5 gallon bucket, then time the pond fill and scale up.
Worked example: a 12 × 8 ft pond, 2.5 ft deep
- Surface area: 12 × 8 = 96 ft².
- Volume: 96 × 2.5 = 240 ft³.
- Gallons: 240 × 7.48 = 1,795 gallons, or about 6,796 liters.
- Pump: to turn the pond over every one to two hours, look for 900 to 1,800 gallons per hour at the height your pump has to lift the water.
Questions
How many gallons are in a cubic foot of water?
7.48 US gallons. A cubic foot of fresh water weighs about 62.4 lb, so one gallon weighs 8.34 lb.
What size pump do I need for my pond?
A common guide is to circulate the full volume once every one to two hours, and once an hour for koi ponds and ponds with a waterfall. Pump ratings fall as the lift increases, so check the flow at your head height, not the maximum on the box.
Why do I need the pond volume?
Water treatments, dechlorinator, salt and fish medication are all dosed per gallon, and filters, pumps and UV clarifiers are sized by volume. Stocking guides for koi and goldfish are given in gallons per fish as well.