PondTools

Surface area tools

These numbers are typed in. Trace your pond once and every calculator uses its measured volume and depths.

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Aeration sizing

Air flow you need
Not calculatedCFM

De-icer wattage

De-icer size
Not calculatedW

Gas-exchange stocking limit

Total length of fish it can hold
Not calculatedin
How it works

These are rules of thumb. Filtration, how many fish you keep, the weather and the circulation you already have all change what a pond actually needs. Check the equipment ratings and test the water before you rely on these numbers.

CFM = surface area (sq ft) ÷ K K = 750 cool  ·  500 warm  ·  300 hot
watts = surface area (sq ft) × W, rounded up to the next common de-icer size W = 7 mild  ·  10 cold  ·  15 severe
max inches = surface area (sq ft) ÷ D D = 1 goldfish-type  ·  3 koi

The aeration figure assumes a still ornamental pond with a moderate number of fish and a pump of at least 1 CFM. Heavy stocking or algae can raise the demand.

The de-icer size assumes a sheltered site and only aims to keep a hole open for gas exchange. It does not size a heater for the whole pond, and a windy site may need more wattage. The largest size listed here is 3,000 W, so a pond that needs more than that takes two or more de-icers. Go by the manufacturer’s rating.

The stocking figure only looks at gas exchange at the surface. It leaves out filtration, feeding and how much waste the bacteria can handle. Stay under it and test the water.

Want the precise number?

Type your measurements in above for a quick estimate. For the real volume, trace your pond on a photo or satellite image and set its depths. PondTools measures the actual outline, so dosing, liner and pump sizes come out right.

Measure my pond precisely