What Size Liner for a 20 x 16 ft Pond (3 ft Deep)?
A 20 x 16 ft pond at 3 ft deep needs about a 28 x 24 ft EPDM liner (672 sq ft) and matching underlayment. It holds roughly 7,181 gallons.
Quick answer
A 20 x 16 ft pond dug to 3 ft deep needs about a 28 x 24 ft liner, which is 672 square feet. Order matching underlayment the same size, and choose fish-safe EPDM. This pond holds roughly 7,181 gallons.
Liner and volume for a 20 x 16 x 3 ft pond
| Measurement | Value |
|---|---|
| EPDM liner size | 28 x 24 ft |
| Liner area | 672 sq ft |
| Underlayment (same size) | 28 x 24 ft |
| Approx. volume | 7,181 gal |
A liner has to run down one wall, across the bottom, up the far wall, and leave material to anchor the edge, so it is always larger than the pond surface. For a 20 x 16 ft pond at 3 ft deep, that works out to about a 28 x 24 ft sheet, or 672 square feet.
How the Liner Size Is Calculated
The formula adds twice the depth to each dimension, because the liner drops down both walls, plus about a foot of overlap on each edge to anchor it. For this pond that is 20 + (2 x 3) + 2 = 28 ft long and 16 + (2 x 3) + 2 = 24 ft wide, a total of 672 square feet. Liner comes in fixed widths, so round up to the next stocked sheet rather than cutting it close. Always use the maximum depth, not the average, since the liner must physically reach the deepest point.
EPDM, Underlayment, and What It Holds
Fish-safe EPDM rubber is the durable standard: a flexible 45 mil membrane that molds to curves and shelves and lasts decades, and the fish-safe grade is non-toxic to koi. Always lay underlayment beneath it, ordered to the same 28 x 24 ft size, to cushion the liner from stones and roots. At 20 x 16 ft and 3 ft deep this pond holds roughly 7,181 gallons, which suits about 28 koi. With at least 3 feet of depth it is genuine koi water.
Liner gear for a 20 x 16 ft pond
Fish-safe 45 mil rubber, the durable standard.
Order the same 28 x 24 ft size.
For joins and patch repairs.
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Frequently Asked Questions
What size liner for a 20 x 16 ft pond 3 ft deep?
About a 28 x 24 ft liner, or 672 square feet. That is the pond length and width plus twice the depth on each, plus roughly a foot of overlap per edge to anchor it. Round up to the next stocked sheet.
How many gallons is a 20 x 16 x 3 ft pond?
Roughly 7,181 gallons, using length times width times depth times 7.48 gallons per cubic foot. Sloped sides and shelves reduce the real number a little, so treat this as a rectangular maximum.
Do I need underlayment for a 20 x 16 ft pond?
Yes, always. Order underlayment in the same 28 x 24 ft size as the liner. The geotextile fabric cushions the liner from sharp stones, roots, and settling soil that would otherwise puncture it over the years.
Is a 20 x 16 ft pond big enough for koi?
Yes. At about 7,181 gallons and 3 feet deep it meets the usual koi minimum of 1,000 gallons with a 3-foot deep zone for overwintering. Stock conservatively at around 28 koi.
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