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Pond Liner Size Calculator

Work out the liner size for a pond from its length, width, depth and the edge overlap.

✔ Vet reviewed · 18 Oct 2026Updated 18 Oct 2026Sources: Pure arithmetic / unit conversion on user inputs
Pond Liner Size CalculatorFree · instant
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Quick answer A pond 3 m long and 2 m wide with a 0.8 m maximum depth and 0.3 m of overlap on each side needs a liner about 5.2 m by 4.2 m (3 + 2 × 0.8 + 2 × 0.3 by 2 + 2 × 0.8 + 2 × 0.3). Round up to the next standard size.

How to use the pond liner size calculator

  1. Enter the pond length and width.
  2. Enter the maximum depth and the overlap you want on each side.
  3. Press Calculate.

Worked example

A pond 3 m long, 2 m wide and 0.8 m deep, with 0.3 m of overlap on each side.

Pond length
3 m
Pond width
2 m
Maximum depth
0.8 m
Edge overlap on each side
0.3 m
5.2 m (17.1 ft) × 4.2 m (13.8 ft)
Liner length
5.2 m (17.1 ft)
Liner width
4.2 m (13.8 ft)
Area
21.8 m² (235 ft²)

Round up to the next standard liner size and check with your supplier.

Example values are illustrative; this result is produced by the same calculator above.

How we calculate it

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

Sources: Pure arithmetic / unit conversion on user inputs (no external constant)

Understanding your result

A pond liner must cover the bottom, run up the sides and overlap the edge. The usual calculation adds twice the maximum depth and twice the overlap to both the length and the width.

For a pond 3 m long and 2 m wide with a 0.8 m depth and 0.3 m of overlap, the liner is 3 + 2 × 0.8 + 2 × 0.3 = 5.2 m long and 2 + 1.6 + 0.6 = 4.2 m wide, an area of 21.84 square metres.

Round up to the next standard liner size and check with your supplier, because shelves and uneven edges need extra. The calculator gives the minimum size for a simple shape.

Common mistakes

  • Forgetting the overlap at the edges.
  • Using the average depth instead of the maximum depth.
  • Ignoring shelves and steps in the pond shape.
  • Mixing metres and feet.
  • Ordering exactly the calculated size with no spare.

Good to know

  • Underlay protects the liner from stones and roots.
  • Use the Pond Volume Calculator for the water volume.
  • A fold or two at corners uses extra liner.

Frequently asked questions

How much overlap do I need?

Enough to hold the liner at the edge, plus a margin. Ask your liner supplier; enter your own figure.

Why use maximum depth?

The liner must go down to the deepest point and back up, so each side needs twice the depth.

What shape is this for?

Rectangular or oval ponds, using the pond's longest length and widest width.

Does it work for an irregular pond?

Use the longest length and widest width, and add extra for shelves and curves. Ask your supplier.

Should I add underlay?

Underlay protects the liner, but it does not change the liner size.

What overlap should I enter?

Enough to anchor the liner at the edge. Ask your liner supplier.

Reviewed by a licensed veterinarian
Last reviewed 18 Oct 2026 · How we review

Sources

  1. Pure arithmetic / unit conversion on user inputs (no external constant)
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Estimates only. Every pet is different — confirm with your veterinarian.