Pond Liner Sizing: Measure and Order the Right Size

Quick answer: Measure the pond’s longest length, widest width and deepest point. Liner length = pond length + (2 x maximum depth) + 0.6m, and the same for width. The extra 0.6m gives a 30cm overlap on every edge. Round up to the next available size and order underlay in the same size.

• Formula: pond length or width + (2 x max depth) + 0.6m
• Example: 3m x 2m pond, 0.6m deep = 4.8m x 3.8m, order 5m x 4m
• Example: 6m x 4m koi pond, 1.5m deep = at least 9.6m x 7.6m
• Sizes work either way round: 4m x 5m covers a 5m x 4m need
• Underlay is ordered in the same size as the liner

Last reviewed: 3 October 2026 · Reviewed by the PondLinersco.co.uk team