Pond Volume Calculator — How Many Litres Is My Pond?

Our pond volume calculator works out the water capacity of your pond based on its shape and dimensions, then recommends appropriately sized equipment.

Volume formulas by shape

• Rectangular: Length × Width × Depth × 1,000 litres
• Circular: π × Radius² × Depth × 1,000 litres
• Kidney: Length × Width × Depth × 0.75 × 1,000 litres (approximate shape factor)
• Irregular: Length × Width × Depth × 0.65 × 1,000 litres (approximate shape factor)

The kidney and irregular factors are practical rules of thumb (an inscribed ellipse fills about 78% of its bounding rectangle). For the most accurate result on a complex outline, split the pond into regular sections, work out each one and add them together. Our general volume calculatorhandles cuboid and cylinder shapes and converts straight to litres (1 m³ = 1,000 litres).

Average vs maximum depth

If you enter maximum depth, we estimate the average as 60% of the maximum — a rule of thumb that suits a typical stepped garden pond with marginal shelves and a deeper centre. Bowl-shaped ponds are closer to 40% of the maximum and uniformly sloped ponds about 50%; lower the Max Depth Factor in Advanced Options to match your pond’s profile.

Equipment sizing guide

• Pump: Flow rate = pond volume ÷ 1-2 hours (litres/hr) — turn the full volume over once an hour for fish, once every two hours for a lightly stocked pond
• Filter: Rated for at least the full pond volume
• UV clarifier: roughly 1 watt per 450 litres for a standard pond (a common industry rule of thumb)

These equipment figures are practical sizing guidelines from UK pond suppliers, not a formal standard. For koi ponds or heavily stocked fish ponds, double the filter rating and UV wattage. Always check manufacturer specifications for equipment at the required head height.