Pond liner calculator
Enter your pond’s length, width and maximum depth to get the liner size: pond size + 2 × maximum depth + 2 × overlap.
Enter your measurements
More options: Spill
- Buy at least
- 16 × 12 ft
- Liner area (also the underlayment)
- 192 sq ft
- Water volume (approx.)
- 529 gal (2,002 L)
- Pump flow (rule of thumb)
- 264–529 gal/hr
Length: 10 ft + 2 × 2 ft deep + 2 × 1 ft overlap = 16 ft
Width: 6 ft + 2 × 2 ft + 2 × 1 ft = 12 ft
Water: 10 ft × 6 ft × 1.5 ft avg × shape factor × 7.48 gal/cu ft ≈ 529 gal
- The pump range assumes moving the whole pond volume once every one to two hours, a common starting point for garden ponds. Fish-heavy and koi ponds are often run faster.
- Waterfalls need flow for their width: pond suppliers suggest roughly 1,500 gallons per hour per foot of spill (100–125 per inch) for an even sheet, about half for a trickle and double for a heavy fall. Pumps lose flow the higher they lift and through bends and filters, so check the maker’s chart at your waterfall’s height.
- Add a protective underlayment (or old carpet) the same size as the liner to guard against stones and roots.
Quick answers for common sizes
| Example | Answer |
|---|---|
| What size liner for an 8×6 pond, 2 ft deep | 14 ft |
Liner size by pond depth (length and width as above)
| Maximum depth | Liner length | Liner width | Buy at least |
|---|---|---|---|
| 1 ft | — | — | — |
| 1.5 ft | 15 ft | 11 ft | 15 × 11 ft |
| 2 ft | 16 ft | 12 ft | 16 × 12 ft |
| 2.5 ft | 17 ft | 13 ft | 17 × 13 ft |
| 3 ft | 18 ft | 14 ft | 18 × 14 ft |
A flexible liner has to go down one side, across the bottom and up the other, then tuck under the edging. The overlap is usually about a foot on each side.
The liner formula
Picture the liner laid across the hole: it runs down one wall, across the floor and up the far wall, then lies flat under the edging. That is the pond length plus twice the depth, plus an overlap at each end. Do the same across the width. Shelves and slopes don’t change the answer — the liner still has to reach the deepest point. Pond-supply maker EasyPro sizes liners the same way: depth twice, plus overhang.
liner length = pond length + 2 × max depth + 2 × overlap liner width = pond width + 2 × max depth + 2 × overlap US gallons ≈ length × width × average depth (ft) × shape factor × 7.48 shape factor: rectangle 1 · oval 0.785 · freeform ≈ 0.7
| Pond (L × W × max depth) | Liner with 1 ft overlap | Approx. gallons (oval, avg ⅔ of max) |
|---|---|---|
| 6 × 4 × 1.5 ft | 11 × 9 ft | ≈ 140 gal |
| 8 × 6 × 2 ft | 14 × 12 ft | ≈ 380 gal |
| 10 × 8 × 2 ft | 16 × 14 ft | ≈ 630 gal |
| 12 × 10 × 3 ft | 20 × 18 ft | ≈ 1,410 gal |
The 8 × 6 ft row is worked through in full, with stock sizes and the dig, on What size liner for an 8×6 pond, 2 ft deep.
Tips
- Measure the hole after digging, not the plan — holes grow.
- Choose a liner sold as fish- and plant-safe. EPDM rubber (often 45 mil) is a common choice for its flexibility; reinforced polyethylene is lighter.
- Fold pleats neatly at corners rather than cutting; don’t trim the overlap until the pond has been filled and settled.
- Check local rules on pond depth and fencing — some places treat deeper water features like pools.
- Top the pond up with rainwater rather than chlorinated tap water where you can: one inch of rain on a small shed roof is around 65 gallons after losses — see How much rainwater from a 10×12 shed roof.
What you’ll need
- EPDM pond liner (fish-safe)Premium price
Flexible rubber liner that folds into curves and shelves. Check the size against the calculator before ordering — stock sizes step up in whole feet.
See options on Amazon (opens in a new tab) - Pond liner underlaymentMid-range price
A felt layer under the liner that protects it from stones and roots. Buy the same size as the liner.
See options on Amazon (opens in a new tab) - Square-point transfer shovelBudget price
Flat blade for scooping gravel, soil and sand off a driveway pile — a round shovel leaves too much behind.
See options on Amazon (opens in a new tab)
As an Amazon Associate we earn from qualifying purchases. Links to products are affiliate links — they cost you nothing extra and help keep these calculators free.
Frequently asked questions
What size liner for an 8 × 6 pond 2 ft deep?
14 × 12 ft with 1 ft of overlap on each edge. The full example, with gallons and stock sizes, is on What size liner for an 8×6 pond, 2 ft deep.
How much overlap should a pond liner have?
Commonly about 1 ft (30 cm) on each side, enough to tuck under edging stones and anchor. Some builders leave more and trim after the pond has been filled and settled.
What size pump for a pond waterfall?
Size it on the spill width: a common starting point is about 1,500 gallons per hour per foot of spill (100–125 per inch) for an even sheet of water, half that for a trickle and double for a heavy fall. Enter the spill width under More options, and check the pump’s flow chart at the height it has to lift.
How many gallons is my pond?
For a rectangle, length × width × average depth in feet × 7.48 (a cubic foot holds about 7.48 gallons). For an oval, multiply by about 0.785 as well. An 8 × 6 ft oval pond averaging 1.33 ft deep holds roughly 375 gallons.
Related guides
Sources
- EasyPro Pond Products — What do I need to know about pond liners (opens in a new tab) — Liner sizing: add the depth twice to the length and width, then add overhang; EPDM for water gardens; install over protective underlayment.
- Webb’s Water Gardens — Pond Pump Sizing Guide (opens in a new tab) — Waterfalls: about 1,500 gph per foot of width (≈125 gph per inch) as a common residential starting point.
- smartpond — Planning to Build a Waterfall (opens in a new tab) — 100 gph per inch of spillway for a sheet of water; half for a trickle, double for a heavy flow; bends and filters reduce flow.