Skip to content
Generated on: July 20, 2026 at 09:33 PM

Pond Liner Calculator

Inputs

Pond length3 m
Pond width2 m
Pond depth0.6 m
Edge overlap30 cm

This is an estimate that assumes a rectangular pond with vertical walls. Sloped banks, planting shelves, and irregular outlines all increase the liner required. Measure the deepest point and add extra material before cutting, since a liner cannot be made larger after installation.

Generated with OneCalc · https://onecalc.app/en/lifestyle/pond-liner

Lifestyle

Pond Liner Calculator

Size a flexible pond liner from the pond length, width, and depth, including the overlap needed to anchor the liner past each edge.

Inputs

≥ 0 m
≥ 0 m
≥ 0 m

Results

Enter a value to see results.

A 3 m × 2 m pond 0.6 m deep with 30 cm of overlap needs a liner about ... by ..., or ... of material.

Embed this calculator

Preview

Paste this code into your page to show the calculator.

Share this calculation

Anyone who opens this link sees your values already filled in.

Pond Liner

A pond liner is a single flexible sheet that holds water in a garden pond, and its size is set by the pond's length, width, and depth, plus an overlap that anchors the liner past each edge. This calculator returns the liner length, width, and total area so a sheet can be ordered without running short at the walls or the rim.

The length + 2×depth + 2×overlap rule

A liner does not simply cover the pond's plan area. It must lie across the bottom, rise up both opposing walls, and then continue past each edge so the surplus can be buried or weighted down. Each dimension therefore gains two wall heights and two overlaps:

l=L+2D+2ow=W+2D+2o\begin{aligned} l &= L + 2D + 2o \\ w &= W + 2D + 2o \end{aligned}

where LL and WW are the pond length and width, DD is the depth, and oo is the overlap on each side. The depth is counted twice because the liner climbs one wall on each side, and the overlap is counted twice for the same reason. The total sheet area is then the product of the two finished dimensions:

A=l⋅w\begin{aligned} A &= l \cdot w \end{aligned}

Why the overlap matters

The overlap is the flap that extends beyond the rim. It is folded back and held down by soil, paving, or rocks so the liner cannot slide into the pond as it fills with water. Too little overlap and the edge can pull loose under the weight of the water; a margin of 20–30 cm8–12 in on every side is common, and more is sensible on soft or sloping banks.

Worked example

Consider a pond 3.4 m long and 2.1 m wide, 0.55 m deep, with a 0.25 m overlap on each side:

l=3.4+2(0.55)+2(0.25)=5.0 mw=2.1+2(0.55)+2(0.25)=3.7 mA=5.0⋅3.7=18.5 m2\begin{aligned} l &= 3.4 + 2(0.55) + 2(0.25) = 5.0 \ \text{m} \\ w &= 2.1 + 2(0.55) + 2(0.25) = 3.7 \ \text{m} \\ A &= 5.0 \cdot 3.7 = 18.5 \ \text{m}^2 \end{aligned}

Consider a pond 10 ft long and 7 ft wide, 24 in (2 ft) deep, with a 12 in (1 ft) overlap on each side:

l=10+2(2)+2(1)=16 ftw=7+2(2)+2(1)=13 ftA=16⋅13=208 ft2\begin{aligned} l &= 10 + 2(2) + 2(1) = 16 \ \text{ft} \\ w &= 7 + 2(2) + 2(1) = 13 \ \text{ft} \\ A &= 16 \cdot 13 = 208 \ \text{ft}^2 \end{aligned}

The result assumes vertical walls; sloped sides and planting shelves follow a longer path, so add a margin before cutting. To work out how much water the finished pond will hold, see Swimming Pool Volume Calculator.

Frequently Asked Questions (FAQ)

How big should a pond liner be?

A liner must reach across the pond floor, up both opposing walls, and far enough past each edge to be anchored. The length is the pond length plus twice the depth plus twice the overlap, and the width follows the same rule. For a 3 × 2 m pond 0.6 m deep with 0.3 m of overlap, the liner is 4.8 × 3.8 m, or about 18.2 m².

A liner must reach across the pond floor, up both opposing walls, and far enough past each edge to be anchored. The length is the pond length plus twice the depth plus twice the overlap, and the width follows the same rule. For a 10 × 6.5 ft pond 2 ft deep with 1 ft of overlap, the liner is 15.7 × 12.5 ft, or about 196 ft².

Why does the liner need an overlap past the edge?

The overlap is the flap of liner that extends beyond the pond rim. It is folded back and buried under soil, paving slabs, or rocks so the liner is held firmly in place and cannot slip into the water as the pond fills. Without an adequate overlap the liner can pull away from the bank, so a margin of at least 20–30 cm on every side is common.

The overlap is the flap of liner that extends beyond the pond rim. It is folded back and buried under soil, paving slabs, or rocks so the liner is held firmly in place and cannot slip into the water as the pond fills. Without an adequate overlap the liner can pull away from the bank, so a margin of at least 8–12 in on every side is common.

Does the formula assume vertical walls?

The length + 2 × depth term assumes the liner drops straight down each wall. Most garden ponds have sloped or shelved sides, so the liner follows a slightly longer path down the slope than the vertical depth. The straight-wall result is therefore a minimum; sloped sides and planting shelves consume extra material, so add a margin before cutting.

Disclaimer

This is an estimate that assumes a rectangular pond with vertical walls. Sloped banks, planting shelves, and irregular outlines all increase the liner required. Measure the deepest point and add extra material before cutting, since a liner cannot be made larger after installation.

Recommended Next

Swimming Pool Volume Calculator

Calculate the water volume of a rectangular or round swimming pool in gallons or litres from its dimensions and average depth.

 Learn more
Rainwater Harvesting Calculator

Estimate the volume of rainwater collectible from a roof catchment area given a rainfall depth and collection efficiency.

 Learn more
Concrete Volume Calculator

Calculate how much concrete you need for a slab. Enter dimensions and waste factor to get the total volume and the number of 40 kg or 25 kg bags.

 Learn more

200+ calculators · 10 languages · 100% free

Was this calculator helpful?

No

How can we improve this calculator?
Powered by OneCalc ↗