How to calculate pond volume
Surface area × average depth gives cubic feet; multiply by 7.48 for US gallons.
For round ponds the area is π × radius², and for oval ponds π ÷ 4 × length × width. For irregular ponds, pick the closest shape and use the average length and width.
Gallons in common pond sizes
| Pond | Average depth | Gallons |
|---|---|---|
| 6 × 4 ft rectangle | 1.5 ft | 269 |
| 10 × 6 ft rectangle | 2 ft | 898 |
| 8 ft round | 2 ft | 752 |
| 12 × 8 ft oval | 2 ft | 1,128 |
| 15 × 10 ft rectangle | 2.5 ft | 2,805 |
| 20 × 12 ft oval | 3 ft | 4,230 |
Why gallons matter
Water treatments, fish stocking, pumps and UV filters are all sized by volume. An accurate gallon figure keeps doses right and avoids buying a pump that is too small.
Filling or treating a swimming pool instead? Use the pool volume calculator.
Pool volume calculatorFrequently asked questions
How do I calculate pond gallons?
Multiply the surface area by the average depth to get cubic feet, then by 7.48. A 10 × 6 ft pond averaging 2 ft deep holds 120 cu ft × 7.48 = about 900 gallons.
How do I measure the average depth of a pond?
Pond floors are rarely flat. Measure the depth at several points (edges, shelves and the deepest part) and average them. Plant shelves can take a big bite out of the volume.
What size pump does my pond need?
Pump flow is rated in gallons per hour (gph). The calculator shows the flow needed to move the whole volume once an hour and once every two hours; your pump or filter maker states which turnover they recommend.
