Pond Calculators & Tools
Free, practical calculators for keeping a goldfish or koi pond — size the pond, check stocking density, size the filter, work out feeding amounts, plan water changes, and size a pond liner.
Pond Volume Calculator
Work out how many gallons or litres your pond holds from its shape and dimensions — rectangular, round, oval, or an irregular naturalistic shape
Fish Stocking Density Calculator
Check your total fish length against your pond volume to see whether it's comfortably stocked, crowded, or has room for more — separate guidance for goldfish and koi
Filter Turnover (GPH) Calculator
Convert your pond volume and a target turnover time into the pump flow rate, in gallons per hour, your filtration needs to keep up with
Feeding Amount Calculator
Scale a daily feeding amount to your fish's total weight and the water temperature — goldfish and koi eat far less, or not at all, once the water turns cold
Water Change Calculator
Work out exactly how much water to remove and replace for a given percentage change, in gallons and in bucket-loads
Pond Liner Size Calculator
Size the liner sheet you need to buy from your pond's length, width, and depth, with the standard overlap allowance, before you break ground