Pond Volume Calculator
Calculate your garden pond’s volume in litres, UK gallons, and cubic metres. Works for rectangular, circular, oval, and irregular ponds — with fish stocking and pump size guidance built in.
Pond Volume Calculator
Select your pond shape and enter dimensions to calculate volume
Maximum length of your pond
Maximum width of your pond
Diameter (width across the centre) of your circular pond
Average depth — measure in a few spots and take the mean
Your Pond Results
Volume, stocking, and equipment guidance
Select your pond shape, enter the dimensions, and click Calculate to find out your pond’s volume in litres, gallons, and m³.
Pond Volume FAQ
Everything you need to know about measuring pond volume and putting the numbers to use.
For a rectangular pond: Volume (litres) = Length (m) × Width (m) × Depth (m) × 1000. For a circular pond: Volume = π × radius² × Depth × 1000. For an oval pond: Volume = π × (Length/2) × (Width/2) × Depth × 1000. For irregular ponds, multiply length × width × average depth × 0.85 × 1000 as an estimate.
As a general rule, allow 45–55 litres per centimetre of fish length for goldfish, and around 1,000 litres per koi carp. So a pond with 5,000 litres could comfortably support five koi or approximately 90 cm worth of goldfish. Always account for future fish growth when planning stocking levels.
A pond pump should circulate the entire pond volume at least once per hour. For a pond with fish, aim for 1.5–2× turnover per hour. For example, a 5,000-litre pond with fish would need a pump rated at 7,500–10,000 litres per hour. Always check the pump’s head height rating against your actual setup.
A minimum depth of 60 cm (2 ft) is recommended for most UK garden ponds to prevent complete freezing in winter. For koi ponds, a depth of 1.2–1.5 m (4–5 ft) is advised to give fish adequate space and stable water temperature. Shallower marginal shelves of 20–30 cm are ideal for planting.
For irregular ponds, measure the maximum length and maximum width, then multiply by a shape factor of 0.85 (a standard correction for non-rectangular shapes). Multiply by average depth and 1000 to get litres. You can estimate average depth by taking several measurements around the pond and averaging them.
A UK (Imperial) gallon equals 4.546 litres, while a US gallon equals 3.785 litres. When buying pond products or pumps in the UK, always use Imperial gallons unless the product specifies otherwise. This calculator shows both, clearly labelled.
Treatment dosages vary by product — always follow the manufacturer’s instructions. This calculator gives you your pond volume so you can multiply it by the product’s recommended dose per litre. Common treatments like dechlorinators typically dose at 1 ml per 100 litres, while algae treatments vary widely.