What Size Pond Liner Do I Need? (2026 Guide)

The sizing formula, step by step

A liner must cover the floor, climb both walls and lap past the rim, so every dimension gets the depth added twice plus overlap twice. We'll size a 10×6 ft pond dug 2 ft deep with 1 ft of overlap on each side.

1. Add the depth twice

The liner runs down one wall, across the floor and up the other wall, so the depth counts on both sides: 2 × 2 = 4 ft added to the length and the width.

2. Add the overlap twice

You want the liner to lap past the rim so it can be tucked under rocks or soil and held in place. At 1 ft per side that's 2 × 1 = 2 ft more on each dimension.

3. Work the example

Length: 10 + 4 + 2 = 16 ft. Width: 6 + 4 + 2 = 12 ft. So a 10×6×2 ft pond takes a 16×12 ft liner, and 16 × 12 = 192 sq ft of material — a piece you can cut from a 15×20 ft roll with room to spare. The pond liner calculator does this math for any pond size in seconds.

Liner sizes for common ponds

Every size below uses 1 ft of overlap per side. Pick the row for your pond and read the liner size at your dig depth:

Check the pattern: the 10×6 ft pond needs a 16×12 ft liner at 2 ft deep, but an 18×14 ft liner at 3 ft deep. Every extra foot of depth adds 2 ft to each dimension, so a deep pond grows fast — dig 1 ft deeper and the liner gains 2 ft in length and 2 ft in width.

Irregular ponds: how to size the liner

Most ponds aren't clean rectangles. The reliable approach is to split the footprint into rectangles, take the longest overall length and the widest overall width, then add the depth-plus-overlap allowance to both — in other words, size off the smallest rectangle that fully contains the pond.

For a kidney- or freeform-shaped pond, measure the longest and widest spans and add the same allowances. If the sides slope steeply, the water is deeper toward the middle than at the shelves: use an average depth leaning toward the deep end, or better, size from your deepest point and let the shallow areas simply have more spare liner. You can always fold and trim the excess — you can't stretch a short liner.

Buying and install tips

• Buy big and trim to fit — cutting or folding a liner a few inches too large is easy; patching or splicing one that's short is not. Suppliers sell EPDM in standard roll widths that you cut to length.
• EPDM 45 mil is the DIY workhorse — 45 mil rubber is the most common thickness for home ponds: flexible enough to drape corners and steps, and rated to last for decades in the sun.
• Clear and cushion the base first — pull out roots and sharp stones, then lay an underlayment or a thin sand bed so the liner never sits directly on a pointy spot.

Once the liner is sized, work out the water volume for pumps and treatments with our pool gallons guide, and if the pond sits beside a drainage trench, check how much gravel a french drain needs while you're at it.

Calculate your exact liner size →