Pond Volume Calculator
Choose your pond’s shape, enter its dimensions, and get the water volume in gallons, litres, and cubic feet — the first number every other pond calculation starts from.
Estimated pond volume
How the estimate works
A rectangular pond’s volume is simply length × width × average depth. A round pond is treated as a circle from its diameter, and an oval pond uses the ellipse-area formula from its length and width. All three convert cubic feet to gallons at 7.48052 gallons per cubic foot, and gallons to litres at 3.785411784 litres per gallon.
An irregular, naturalistic pond with curved or kidney-shaped edges rarely fills its bounding rectangle, so the calculator applies a 0.75 correction factor to the length × width × depth box — a widely used planning estimate for ponds that don’t match a clean geometric shape.
Frequently Asked Questions
Why does pond volume matter so much?
Almost every other pond-keeping decision starts from volume — how many fish it can support, how big a filter pump you need, how much water to change, and how much dechlorinator or treatment to dose. Get the volume wrong and every downstream calculation is wrong too.
How accurate is a shape-based estimate?
For a true rectangle, oval, or circle it's close to exact, since those are standard geometric formulas. For an irregular, naturalistic pond with curved edges, a bounding length x width x depth box is reduced by a 0.75 correction factor, which is a widely used planning estimate — the true volume can still vary, especially with shallow marginal shelves.
Should I measure the deepest point or the average depth?
Use the average water depth across the whole pond, not the single deepest point. If your pond has a deep zone and a shallow shelf, estimate the average depth across the full footprint — averaging a few measurements at different spots gets you close.
Why do gallons and litres come out to different-looking numbers?
They're just two units for the same volume: 1 US gallon is about 3.785 litres. The calculator reports both so you can use whichever your pump, dosing product, or local suppliers are labelled in.
Planning tool only. Results are geometric estimates rounded for display; for an irregular pond, treat the figure as a starting point and re-check it against how much water it actually takes to fill.