How to use the pond liner calculator
- Measure the longest length and widest width of the pond, even if it is curved.
- Measure the deepest point.
- Choose the edge overlap, usually 1 to 2 ft per side.
- Read the liner size, the nearest stock size, and the pond volume and pump size.
Pond liner formula
Liner length = pond length + 2 × depth + 2 × overlap
Liner width = pond width + 2 × depth + 2 × overlap
Gallons ≈ length × width × depth × shape factor × 7.48
Worked example
A 10 × 8 ft pond, 2 ft deep, 1 ft overlap
- Liner length = 10 + 4 + 2 = 16 ft; width = 8 + 4 + 2 = 14 ft.
- Liner = 16 × 14 ft (224 sq ft), with the same size underlayment.
- Volume ≈ 10 × 8 × 2 × 0.85 = 136 cu ft = 1,017 gallons; pump about 500 to 1,000 gph.
Liner sizes for common ponds (1 ft overlap)
| Pond | Depth | Liner |
|---|---|---|
| 6 × 4 ft | 1.5 ft | 11 × 9 ft |
| 8 × 6 ft | 2 ft | 14 × 12 ft |
| 10 × 8 ft | 2 ft | 16 × 14 ft |
| 12 × 10 ft | 2.5 ft | 19 × 17 ft |
| 15 × 12 ft | 3 ft | 23 × 20 ft |
Common mistakes to avoid
- Measuring the average depth. Use the deepest point for the liner.
- No underlayment. Stones and roots puncture liners from below.
- Too little overlap. Liner edges that shrink back cause leaks at the rim.
- Trimming before filling. Fill the pond first, let the liner settle, then trim.
Frequently asked questions
How do I calculate pond liner size?
Liner length = pond length + 2 × max depth + 2 × overlap. Liner width = pond width + 2 × max depth + 2 × overlap. A 10 × 8 ft pond, 2 ft deep with 1 ft of overlap, needs a 16 × 14 ft liner.
How much overlap should a pond liner have?
At least 1 ft around the edge, and 2 ft if you want to bury it under rocks or turf or adjust the edges later.
Do shelves change the liner size?
No. The liner follows shelves and slopes, but the 2 × depth allowance already covers them as long as you measure the maximum depth.
How many gallons is my pond?
Length × width × depth × 7.48, multiplied by a shape factor for sloped sides: about 0.85 for rectangular, 0.67 for oval and 0.6 for natural shapes. A 10 × 8 × 2 ft rectangular pond holds about 1,000 gallons.
What size pump do I need?
Most ponds aim to circulate the full volume every 1 to 2 hours, so a 1,000 gallon pond needs roughly 500 to 1,000 gallons per hour at the height it pumps to.