Pond Liner Calculator: What Size Liner Do I Need
The pond liner calculator turns four measurements into the flexible liner you need to buy. Enter the pond length and width at the water line, the deepest point, and the flat overlap you want on each edge. It returns the liner length and width, the total liner area in square feet, and a rough water volume in US gallons.
How to size a pond liner
- Enter the Pond length in feet, measured across the water surface.
- Enter the Pond width in feet at the surface.
- Set the Max depth to the deepest point of the pond.
- Set the Overlap per edge (2 ft is the default flat margin).
- Read the Liner size, Liner area and Water volume tiles that update as you type.
- Click Copy estimate to save the liner size, area and volume.
Examples
10 by 6 ft pond, 2 ft deep, 2 ft overlap
Length 10, width 6, depth 2, overlap 2
18 by 14 ft liner, 252 sq ft, about 538.56 gallons
8 by 5 ft pond, 1.5 ft deep, 1 ft overlap
Length 8, width 5, depth 1.5, overlap 1
13 by 10 ft liner, 130 sq ft, about 269.28 gallons
12 by 8 ft pond, 3 ft deep, 2 ft overlap
Length 12, width 8, depth 3, overlap 2
22 by 18 ft liner, 396 sq ft, about 1292.54 gallons
Frequently asked questions
What size pond liner do I need?
Add twice the maximum depth and twice the edge overlap to each of the pond length and width. For a 10 by 6 ft pond that is 2 ft deep with a 2 ft overlap, the liner works out to 18 by 14 ft, which is 252 square feet of material.
Why add twice the depth to the liner size?
A flexible liner has to drop down one wall to the bottom and rise up the opposite wall, so every dimension gains the depth twice. The overlap is then added to both edges so there is enough flat liner to weigh down and hide.
How much overlap should I leave on each edge?
Around 1 to 2 ft per edge is typical, and the calculator uses 2 ft by default. That margin gives you enough flat liner to anchor under rocks, soil or paving, and it leaves room for the ground to settle without pulling the liner into the water.
How is the water volume estimated?
It multiplies the surface area by an average depth of 60 percent of your maximum depth, then converts cubic feet to US gallons at 7.48 gallons per cubic foot. Real ponds have sloped sides and shelves, so they hold less than a full box, which is why this figure is only an approximation.
What units does the calculator use?
Everything is in feet. Length, width, depth and overlap are entered in feet, the liner area is reported in square feet, and the water volume is reported in US gallons. Convert metric measurements to feet before entering them.
Does it account for planting shelves or sloped sides?
No. For the liner size it treats the pond as a simple box so the material is never too short at the deepest point. Shelves and slopes do not change how much liner you need, but they do mean the pond holds less water than the box volume.
Should I round up to a stock liner size?
Yes. Liners are sold in set sizes, so round the calculated length and width up to the next size a supplier stocks. A little extra liner is easy to trim, and it protects you against small measuring errors and uneven ground.
Do I still need an underlay under the liner?
This tool only sizes the liner itself, but an underlay or protective fleece is strongly recommended. Buy the underlay in the same finished dimensions as the liner so it fully cushions the material against roots and sharp stones.
Is anything I enter sent to a server?
No. The calculation runs entirely in your browser, so the dimensions you type never leave your device. Nothing is uploaded, stored or logged.
Learn more
- How to measure and size a pond liner
Measure a garden pond correctly, apply the twice depth plus overlap rule, and buy the right liner and underlay the first time.
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