Pond Liner Size Calculator
Get the flexible pond liner length and width from your pond size, depth and overlap — plus the approximate water volume.
How it works
Liner length = pond length + 2 × depth + 2 × overlap · Liner width = pond width + 2 × depth + 2 × overlap · Volume (gal) ≈ L × W × depth × 0.85 × 7.48
A flexible liner has to drop down the sides, cross the bottom, and climb back up — so each dimension grows by twice the depth, plus an overlap to anchor the liner around the rim under rocks or soil. The classic rule is length + 2×depth + 2×overlap by the same for the width. Water volume uses a 0.85 factor because real ponds have sloping sides and shelves, holding less than a perfect box; 7.48 converts cubic feet to US gallons.
Worked example
A 10 × 6 ft pond, 2 ft deep, with 1 ft of overlap needs a liner 10 + 4 + 2 = 16 ft long and 6 + 4 + 2 = 12 ft wide — 192 sq ft. It holds about 10 × 6 × 2 × 0.85 × 7.48 ≈ 763 gallons.
Frequently asked questions
How do I measure for a pond liner?
Take the pond length, width and maximum depth. Liner length = length + twice the depth + twice your overlap; liner width uses the same formula. The overlap (about 1 ft) is what you tuck and weight down around the edge.
What overlap should I leave?
Leave roughly 6–12 inches beyond the pond edge all the way around so you can secure the liner with rocks, soil or edging and stop it slipping into the water as it settles.
Is the water volume exact?
No — it is an estimate that assumes sloped sides and planting shelves, which is why it applies a 0.85 factor. Irregular shapes and steep or shallow profiles will vary, so treat it as a guide for pumps and treatments.
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This calculator is for educational purposes. Double-check important results before acting on them.