Pond liner calculator & estimator
Get the exact pond liner you need in seconds with our pond liner calc. Enter your pond's length, width and maximum depth in metres — the pond liner estimator adds the drape, overlap and edge allowance, then shows you the sheet size, area and indicative price for our 0.7 mm RPM liner.
Find the exact liner size in 10 seconds.
Enter your pond's dimensions. We'll add the correct overlap so you fit it once, properly.
Your pond dimensions
Recommended liner
Liner size
12.20 × 12.20 m
Total area
148.8 m²
Pond volume
60,000 L
Indicative price
£1332
How the pond liner calculator works
A pond liner is a single flat sheet that has to drape down both sides of the excavation, cover the bottom, and then carry on far enough to be anchored at the edge. So the sheet is always meaningfully larger than the surface of the pond itself. The calculator turns three numbers — length, width and maximum depth — into the exact sheet size you need to order.
The formula is straightforward. The liner length equals the pond length plus twice the maximum depth plus the edge overlap on both sides. The liner width follows the same pattern: pond width, plus twice the depth, plus overlap. We default to 0.5 m of overlap per side, which is enough to tuck securely under coping stones, turf or a pebble beach edge. Multiplying the resulting length and width gives the total area in square metres, which we use for the indicative price.
Worked example. A common UK garden pond of 4 × 3 m at 0.6 m deep needs a liner of 4 + (2 × 0.6) + 1.0 = 6.2 m long by 3 + (2 × 0.6) + 1.0 = 5.2 m wide. That works out at roughly 32 m² of RPM 0.7 mm — one factory sheet, no welding required.
Building something smaller? Our small pond liners guide has a size chart for common 1 × 1 m to 3 × 3 m garden and wildlife ponds.
Commercial & large-scale applications. The same formula scales to lined reservoirs, lagoons and lakes — the only difference is that panels are pre-welded in our workshop and joined on site. For sizing guidance at that scale, see our commercial pond liner applications hub, covering agricultural, golf-course and lake installs.