Pond Liner Calculator

Enter your pond's length, width and deepest point and get the liner and underlay size to buy, with edge overlap, in feet or metres.

Yard & GardenWorldwideSource: Liner sizing formula (length + 2 × depth + 2 × overlap)Free, no sign-up

Units

Pond length (ft)

Longest point.

Pond width (ft)

Widest point.

Maximum depth (ft)

Edge overlap each side (ft)

All Pond Solutions uses 2 ft (0.6 m).

Price per ft² (optional)

Measure the hole as dug, at its longest, widest and deepest points. The result updates as you type.

Liner size

20 × 18 ft

360 ft² of liner (and the same of underlay)

Length	10 + 2 × 3 + 2 × 2 = 20 ft
Width	8 + 2 × 3 + 2 × 2 = 18 ft

What this page cannot tell you

Which liner material or thickness to use, or how a liner folds into corners and shelves. Liners come in stock sizes — round up to the next size you can buy. Very irregular ponds may need more.

How to work out pond liner size

Measure the longest length. End to end at the widest point of the hole.
Measure the widest width. Side to side.
Measure the deepest point. Even if only one area is that deep.
Set the edge overlap. All Pond Solutions uses 2 ft (0.6 m) each side to anchor the liner.
Read the liner size. Length × width to buy, and the same for underlay.

10 situations where a pond liner calculator helps

Digging a new garden pond

Buy the right liner before you dig too far.

Replacing a leaking liner

Measure the existing hole and get the new size.

Koi ponds

Deeper ponds need much more liner per foot of length.

Wildlife ponds

Shallow, sloped ponds still use the deepest point.

Ordering underlay

Underlay is cut to the same size.

Comparing EPDM and PVC prices

Enter a price per square foot or metre.

Metric liners

Work in metres for liners sold by the metre.

Stream and waterfall pools

Each pool is sized the same way.

Raised ponds

Use the inside height as depth.

Choosing a stock size

Round up to the next size the supplier sells.

How the size is worked out

A flexible liner has to cover the bottom, go down one side and up the other, and lie flat past the edge so it can be held in place. All Pond Solutions gives the formula as overlap + depth + width + depth + overlap for the width, and the same with the length, and says overlap 'should always be 0.6m (2 feet)' so the liner can be secured — otherwise it 'will sink into the pond' when filling. They also advise rounding totals up.

Using the maximum depth on both sides means sloped sides and shelves are covered with some to spare. A 10 × 8 ft pond, 3 ft deep, with 2 ft overlap needs a 20 × 18 ft liner.

Limits: very irregular shapes and steep pleats can need more. Liner material, thickness and UV rating are separate choices. Liners are sold in stock sizes, so round up to the next one available. Everything runs in your browser.

Sources

All Pond Solutions — Calculating the size of your pond liner — Overlap + depth + dimension + depth + overlap; 0.6 m / 2 ft overlap

Frequently asked questions

How do I calculate pond liner size?

Liner length = pond length + 2 × depth + 2 × overlap; liner width = pond width + 2 × depth + 2 × overlap.

What size liner for a 10 × 8 pond?

At 3 ft deep with a 2 ft overlap: 20 × 18 ft.

How much overlap should I leave?

All Pond Solutions uses 2 ft (0.6 m) on each edge; the page lets you change it.

Do I use the average or maximum depth?

The maximum — the liner has to reach the deepest point.

Does underlay need to be the same size?

Yes, it goes under the whole liner.

What if my pond has shelves?

Measure to the deepest point; shelves are covered within that.