Pond Liner Calculator

Enter your pond’s length and width (or diameter) and maximum depth to calculate the liner size you need to buy, in square feet, plus material cost.

Irrigation & WaterUpdated Sep 23, 2026Free, no sign-upInstant results

Shape

Length

Width

Maximum water depth

Use the deepest point — the liner must reach the bottom at the deepest spot plus overlap.

Liner material

Add pricing

Liner price per sq ft

Water cost / 1,000 gal

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Volume: 0
Surface area: 0
Liner size: —

Summary

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Item	Qty	Cost

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Filling tips

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Volume & size

Volume—

Surface area—

Liner size—

Depth—

Liner profile

For a 10 × 8 ft pond with a 2 ft maximum depth and EPDM liner, you need a liner sized 16 × 14 ft (224 sq ft), costing about $190 at $0.85 per sq ft. The same pond holds roughly 1,197 gallons of water.

Liner size by pond dimensions and depth

Sizes include a 2 ft EPDM overlap allowance on every side, measured from the pond’s maximum depth.

Pond liner dimensions and area by pond size
Pond shape & size	Max depth	Liner dimensions (L × W)	Liner area
Small rectangular pond, 6 × 4 ft	1.5 ft	11 × 9 ft	99 sq ft
Rectangular pond, 12 × 10 ft	2.5 ft	19 × 17 ft	323 sq ft
Circular pond, 8 ft diameter	2 ft	14 × 14 ft	196 sq ft
Rectangular pond, 15 × 10 ft	3 ft	23 × 18 ft	414 sq ft
Circular pond, 20 ft diameter	4 ft	30 × 30 ft	900 sq ft
Small rectangular pond, 5 × 5 ft	1 ft	9 × 9 ft	81 sq ft

How to calculate pond liner size

liner length = L + (2 × depth) + overlap; liner width = W + (2 × depth) + overlap; liner sq ft = length × width

Measure your pond's length and width. For a circular pond, use the diameter for both dimensions since liner is sold and cut as a rectangle.
Measure the maximum water depth. Liner must reach the deepest point of the pond, so use the deepest measurement — not an average.
Add depth to both dimensions twice. The liner has to go down one side, across the bottom, and up the other side, so add 2 × depth to both length and width.
Add your material's overlap allowance. Add 1.5-2 ft (depending on liner type) beyond the hole’s edge for anchoring under coping stones or in an edge trench.
Multiply length by width for total area. That final length × width figure is the square footage of liner material to order — round up to the nearest size your supplier stocks.

Worked example

Using the calculator’s defaults: a 10 × 8 ft pond, 2 ft maximum depth, and EPDM rubber liner with a 2 ft overlap at $0.85 per sq ft.

Pond dimensions10 ft × 8 ft
Maximum depth2 ft
Liner length (10 + 2×2 + 2)16 ft
Liner width (8 + 2×2 + 2)14 ft
Liner area (16 × 14)224 sq ft
Estimated liner cost (224 × $0.85)$190.40
Pond water volume (for reference)1,196.9 gal
Estimated fill cost (1,196.9 gal × $4/1,000 gal)$4.79

Choosing a pond liner material

Liner choice affects both durability and price — match it to your pond’s size, budget, and how long you want it to last.

EPDM rubber liner (45 mil)The most durable and widely used pond liner — flexible, UV- and puncture-resistant, and typically rated for 20+ years.
PVC liner (20-30 mil)A budget-friendly option for smaller ponds and water gardens — lighter and easier to work with, but less puncture-resistant than EPDM.
RPE reinforced linerBest for large ponds or sites with sharp rocks and roots — a woven reinforcement layer resists punctures far better than plain rubber or PVC.
Buy a little more than the exact figure.Rocks, roots, and uneven digging rarely match a perfect calculation — rounding up to the next stocked size avoids a second order.
Match thickness to pond size.Small water gardens can get by with thinner PVC, but larger or koi ponds benefit from thicker EPDM or reinforced liner that resists stress from more water weight.

Common mistakes

Using average depth instead of maximum depth.The liner has to reach the deepest point of the pond — sizing from average depth leaves it short where the pond is deepest.
Skipping the overlap allowance.Cutting liner to the exact hole size leaves nothing to anchor at the edges — always add 1.5-2 ft beyond the perimeter.
Forgetting liner needs depth added on both sides.The liner runs down one side and up the other, so depth is added twice to each dimension, not once.
Ordering liner sized to volume instead of dimensions.Liner is sold by square footage of material, calculated from length, width, and depth — not from the pond’s gallon capacity.
Not accounting for underlayment separately.Protective underlayment (geotextile fabric or old carpet) is a separate material and cost from the liner itself, sized the same way.
Choosing liner thickness based on price alone.Thinner liner costs less per square foot but punctures more easily — factor in soil conditions and pond size, not just budget.

What this calculator assumes

Adjust your result if your project differs from these.

Liner size is calculated from the pond’s maximum depth, since the liner must reach the deepest point plus overlap.
Circular ponds are treated as square/rectangular for liner sizing, using the diameter as both length and width — standard practice for cutting flat liner sheets.
Overlap allowance defaults to the selected liner material (2 ft for EPDM and RPE, 1.5 ft for PVC) added to each dimension.
Liner area is length × width of the sized rectangle, not the pond’s actual surface area — some material is trimmed away during installation.
Liner cost is estimated from the price per square foot you enter and does not include underlayment, edging, or installation labor.
Pond water volume is shown for reference using the same dimensions, at 7.48052 gallons per cubic foot.

Common questions

What size liner do I need for a 10 × 8 ft pond?

At a 2 ft maximum depth with EPDM’s 2 ft overlap, you need a liner sized 16 × 14 ft (224 sq ft).

How much overlap should I add to pond liner?

1.5-2 ft beyond the pond’s edge is standard, giving enough material to anchor under coping stones or bury in a perimeter trench.

Do I use average or maximum depth for liner size?

Maximum depth — the liner must reach the pond’s deepest point, so sizing from an average would leave it short there.

How do I size liner for a circular pond?

Use the diameter as both the length and width in the sizing formula, since liner is manufactured and sold as flat rectangular sheets.

How much does pond liner cost per square foot?

EPDM typically runs $0.60-$1.00 per sq ft, PVC $0.30-$0.60, and reinforced RPE $0.80-$1.50, depending on thickness and supplier.

What's the best liner for a large or koi pond?

RPE reinforced liner or thick EPDM (45 mil) hold up best to the water weight and fish activity in larger ponds.

Can I use a smaller liner and just accept a smaller pond?

Not recommended — an undersized liner won’t reach the top edge for anchoring, risking leaks and soil erosion under the liner.

How do I calculate liner for a pond with shelves?

Measure to the maximum depth at the deepest point, and add extra material for the added surface area the shelves create.

Is underlayment included in the liner size?

No — underlayment is a separate material, typically sized the same as the liner (length × width), and priced separately.

How long does pond liner last?

EPDM rubber liner typically lasts 20-30+ years; PVC liner usually needs replacement after 10-15 years.

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