⛲ Pond Volume & Liner Calculator
Enter the length, width and average depth to get the pond volume in litres and gallons, and the liner dimensions to buy.
Volume
3,000 L
792.5 US gal
Liner size
4.6 × 3.6
m (incl. overlap)
Volume = length × width × average depth (1 m³ = 1,000 L = 264 US gallons). Use the average depth for a sloped or irregular pond. Liner size adds twice the depth to each dimension (to line the sides) plus an overlap for the edges: liner = (length + 2×depth + overlap) × (width + 2×depth + overlap). Buy a little extra for folds. 🔒 In your browser.
How the pond volume & liner calculator works
Volume is length × width × average depth: one cubic metre is 1,000 litres or about 264 US gallons. Use the average depth for a sloped or bowl-shaped pond rather than the deepest point. The liner must cover the bottom, up both sides and over the edges, so each dimension gets twice the depth added plus an overlap: liner = (length + 2×depth + overlap) × (width + 2×depth + overlap).
Volume matters for dosing treatments, sizing a pump and filter (aim to turn over the whole volume every 1–2 hours), and stocking fish safely. The rectangular formula slightly overestimates an irregular pond — a common refinement multiplies by about 0.85 for a natural shape. Add extra liner for folds and settling.
Frequently asked questions
How do you calculate pond volume?
Multiply length × width × average depth. In metres that gives cubic metres; ×1,000 for litres, ×264 for US gallons. A 3 × 2 × 0.5 m pond is 3 m³ = 3,000 litres ≈ 793 gallons.
How big a liner do I need for my pond?
Add twice the maximum depth to both the length and the width (to line the sides), plus an overlap of about 30 cm / 1 ft for the edges. So liner length = pond length + 2×depth + overlap, and likewise for width.
Should I use average or maximum depth?
Average depth for the volume, since most ponds are shallower at the edges. Use the maximum depth when sizing the liner, because it has to reach the deepest point up the sides.
Why does pond volume matter?
It sets the dose for water treatments, the pump and filter size (turn the volume over every 1–2 hours), and how many fish you can keep. Under- or over-dosing and undersizing a pump are common mistakes fixed by knowing the volume.
Is the calculation exact for an irregular pond?
The rectangular formula slightly overestimates a curved or natural-shaped pond. A common adjustment multiplies by about 0.85; for an accurate figure, measure the average depth carefully or fill through a metered source.