Pond Volume Calculator: Gallons, Litres and Liner Size
Pick the shape, then enter the dimensions and the average depth. You get the volume in US gallons and litres, the liner size (length + 2 x depth + overlap) and a rough guide to how much fish length the pond can hold.
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Formula
- Rectangular:
volume = length x width x average depth - Round:
volume = pi x (diameter / 2)^2 x average depth - Irregular:
volume = 0.8 x length x width x average depth(0.8 is a typical allowance for a curved outline, not an exact figure) - Gallons: 1 cubic foot = 7.4805 US gallons = 28.316846592 L; 1 US gallon = 3.785411784 L; 1 m3 = 1,000 L
- Liner size:
length + 2 x depth + overlapbywidth + 2 x depth + overlap - Fish stocking rule of thumb: about 1 inch of adult fish per 10 US gallons
Worked example
A rectangular pond 10 ft long, 6 ft wide and 2 ft deep on average:
- Volume = 10 x 6 x 2 = 120 cubic feet = 897.7 gallons (3,398 litres)
- Liner = (10 + 2 x 2 + 2) by (6 + 2 x 2 + 2) = 16 ft by 12 ft
- Fish guide = 897.7 / 10 = about 89.8 inches of adult fish
An 8 ft round pond, 2 ft deep: 3.1416 x 4 x 4 x 2 = 100.5 cubic feet = 752 gallons, with a 14 ft square liner.
A 12 ft by 8 ft pond, 3 ft deep: 288 cubic feet = 2,154 gallons.
Assumptions
- Walls are treated as straight sides, so shelves and slopes are covered by the average depth you enter.
- The irregular factor of 0.8 is a typical rule of thumb.
- The fish guide is a rough rule of thumb, not a limit.
Frequently asked questions
How do I calculate the volume of a pond in gallons?
Multiply length x width x average depth in feet to get cubic feet, then multiply by 7.48 gallons per cubic foot. A 10 x 6 x 2 ft pond is 120 cubic feet, or about 897.7 gallons (3,398 litres).
How do I work out the volume of a round or irregular pond?
For a round pond use pi x radius x radius x depth: an 8 ft diameter, 2 ft deep pond is 3.1416 x 4 x 4 x 2 = 100.5 cubic feet, about 752 gallons. For an irregular pond this calculator takes the longest length x widest width x average depth and multiplies by a typical allowance of 0.8 for the curved outline, so 10 x 6 x 2 ft gives 96 cubic feet, about 718 gallons. It is an estimate; measure average depth at several points.
What size pond liner do I need?
Liner length = pond length + 2 x depth + overlap, and the same for width. For a 10 x 6 ft pond that is 2 ft deep with 2 ft of overlap, the liner is 10 + 4 + 2 = 16 ft by 6 + 4 + 2 = 12 ft. Add more for steep stepped shelves and for edges you want to bury.
How many fish can a pond hold?
A common rule of thumb is about 1 inch of adult fish length per 10 US gallons of water. A 897.7 gallon pond works out to about 89.8 inches of adult fish, for example nine fish of 10 inches. Filtration, aeration, climate and species change the real limit, so treat it as a rough guide and stock gradually.
How many gallons in a 12 by 8 foot pond that is 3 feet deep?
12 x 8 x 3 = 288 cubic feet, and 288 x 7.48 = about 2,154 gallons (8,155 litres). The liner for it would be 20 ft by 16 ft with 2 ft of overlap.
How many gallons in a round pond 10 feet across and 3 feet deep?
The area is 3.1416 x 5 x 5 = 78.5 square feet, so the volume is 235.6 cubic feet, or about 1,762.6 gallons. The liner is 18 ft by 18 ft with 2 ft of overlap.
How many litres in a pond 3 m by 2 m and 0.6 m deep?
Choose metric units. 3 x 2 x 0.6 = 3.6 cubic metres, which is 3,600 litres or about 951 US gallons.