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Pond Liner Calculator — What Size Pond Liner Do I Need?
Calculate the exact pond liner size with depth and overlap allowance for rectangular, circular and kidney-shaped garden ponds.
Longest dimension
Widest dimension
Deepest point of the pond
Protective fleece beneath the liner — strongly recommended
Enter your supplier price for a cost estimate
How We Calculate This
Our pond liner calculator uses the standard pond liner formula to determine the minimum liner size you need, accounting for the pond depth and edge overlap.
The formula
Liner length = Pond length + (2 × Max depth) + 0.6m
Liner width = Pond width + (2 × Max depth) + 0.6m
Liner area = Liner length × Liner width
By pond shape
- Rectangular: Standard formula as above
- Circular: Use diameter for both length and width — liner is always square
- Kidney/irregular: Use maximum length and width measurements — same formula
Key notes
- Overlap: 300mm (12") per side — 600mm total added to each dimension
- Underlay: Same dimensions as the liner
- Liner sizes are rounded up to the nearest 0.5m for purchasing
Frequently Asked Questions
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Last updated: February 2026
Verified against UK standards · estimates only, confirm with your supplier.