🐟 Pond Calculator
Estimate your pond’s water volume and the liner size needed based on length, width, and average depth.
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What this calculator does
The pond calculator estimates the water volume of a garden or backyard pond, plus a suggested liner size, based on the pond’s length, width, and average depth.
The formula
For a rectangular pond, volume equals length × width × average depth. For an oval or round pond, the calculator uses the ellipse area formula, π × (length/2) × (width/2) × depth. The resulting volume in cubic feet is converted to US gallons (1 ft³ ≈ 7.48052 gallons) and liters. Suggested liner dimensions add twice the depth to each side (to reach up and over the pond walls) plus a small overlap allowance for anchoring the liner edge.
- Irregular pond shapes and varying depth will make actual volume differ from this estimate — measure depth at several points and average for better accuracy.
- Liner size suggestions include a basic overlap margin; always round up and check your liner supplier’s sizing guidance.
This tool is for general planning purposes.
Last reviewed August 2026