Pond liner calculator

Enter the pond's length, width and deepest point. You'll get the liner size to buy, the water volume, and a pump size to circulate it.

Pond length (feet)

Pond width (feet)

Maximum depth (feet)

Edge overlap on each side (feet)

–liner size (feet)

Liner area (sq ft): –
Water volume (gallons): –
Pump size (gallons per hour): –

Volume assumes straight sides. Ponds with sloped sides or shelves hold less.

How the math works

A liner has to stretch down one side, across the bottom and up the other side, then lap over the edge. So the liner length is the pond length plus twice the depth, plus the overlap on both ends, and the same for the width. A 10 by 8 foot pond, 2 feet deep, with 1 foot of overlap needs a 16 by 14 foot liner.

Volume is length times width times depth times 7.48, the number of gallons in a cubic foot. That same pond holds up to about 1,200 gallons.

Choosing a pump

A common guideline is a pump that moves the pond's full volume at least once an hour. Fish ponds and ponds with a waterfall usually need more, and pump ratings drop the higher the water has to be lifted, so check the flow chart at your waterfall height.

Common questions

Should I measure an irregular pond at its widest points?

Yes. Measure the longest length and the widest width, even if they're in different places. The extra liner gets folded or trimmed.

Do I need an underlayment?

An underlayment, or a layer of old carpet or sand, protects the liner from rocks and roots. It's cheap insurance compared with finding a leak later.

How deep should a fish pond be?

Two feet is a common minimum for goldfish, and koi ponds are often three feet or more. Deeper water stays cooler in summer and gives fish a place to shelter.