Pond Volume Calculator
Built by Johnny Alto · free, no sign-up · updated July 26, 2026
Enter your pond's dimensions to find how much water it holds in US gallons and liters. Volume is the number that sizes a pump and filter, sets treatment doses, and tells you how many fish the pond can support, so it is worth getting right.
Pond holds about0US gallons
0liters
Use the average depth, not the deepest point, since most ponds shelve. Irregular shapes fall between the rectangular and oval estimates, so measure the average length and width and round sensibly.
How to calculate pond volume
A pond's volume is its surface area times its average depth. For a rectangular pond that is length times width times depth. For a round pond it is pi times the radius squared times depth, and for an oval it is pi times half the length times half the width times depth. Measuring in feet and multiplying gallons by 7.48 per cubic foot gives US gallons; measuring in meters gives cubic meters, which is 1,000 liters each.
The number that trips people up is depth. Most ponds have sloped sides and shelves, so the deepest point overstates the volume. Use the average depth across the whole pond and your estimate will be far closer to reality.
Why pond volume matters
Almost every decision downstream depends on this figure. Pumps and filters are rated by how many gallons they can turn over per hour, water treatments are dosed per gallon, and fish stocking guidelines are set by volume. Get the volume right and everything else falls into place; guess it and you risk an undersized filter or an overdose of treatment.
Recommended gear
Gear for a healthy pond
Frequently asked questions
How do I calculate the volume of my pond?
Multiply the surface area by the average depth. For a rectangular pond in feet, that is length times width times depth, then multiply by 7.48 to get US gallons.
Should I use average or maximum depth?
Use the average depth. Ponds usually have sloped sides and shelves, so the deepest point overstates the true volume.
How many gallons is a 10 by 6 foot pond?
At an average depth of 2 feet, a 10 by 6 foot pond holds about 900 US gallons, or roughly 3,400 liters.
Why do I need to know my pond volume?
Pump and filter sizing, water treatment doses, and fish stocking are all based on volume, so an accurate figure keeps the pond healthy and balanced.
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This calculator gives estimates for planning only; always confirm against your own measurements and species research. Some links are to our buying guides, which contain affiliate links. As an Amazon Associate I earn from qualifying purchases.
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