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Pond & pool calculators
Free, in-browser calculators for garden ponds and swimming pools. Metric and imperial, US and UK gallons.
- Pond volume calculatorGallons and litres for any pond shape, with liner, pump, UV and fish.
- Pool volume calculatorPool volume in US gallons, UK gallons and litres for rectangle, round, oval, kidney and L-shaped pools, with sloped floors and hopper-bottom deep ends.
- Above-ground pool gallons calculatorHow many gallons in an above ground pool: pick a 12–33 ft round or oval size and wall height, or enter your own, for US gallons, litres and UK gallons.
- Pond liner calculatorPond liner size from length, width and deepest depth: liner = length + 2 × depth + 2 × overlap. Feet or metres, rounded up, with underlay and area.
- Pond pump size calculatorPond pump flow rate from pond volume: one turnover every 2 hours for plant ponds, every hour for goldfish, 1.5–2 times an hour for koi. GPH and L/h.
- Pond UV clarifier size calculatorWhat size UV clarifier for your pond: about 1 watt per 75 US gallons for goldfish and plant ponds, 1 W per 50 gal for koi, double to sterilize.
- Pond fish stocking calculatorHow many fish can your pond hold? Goldfish at 10–20 US gallons per inch, koi from 1,000 gal and about 250 gal each, with depth checks for winter and summer.
- Pool fill time calculatorHow long it takes to fill a pool or pond with a garden hose: volume ÷ flow rate. Enter gallons or litres and GPM or L/min; includes top-up from part full.
- Pool turnover calculatorPool turnover time from volume and pump flow, and the GPM needed to turn the pool over in 8 hours or any target. Gallons or litres, GPM or L/min.
- Pool chlorine calculatorHow much liquid chlorine, bleach, cal-hypo, dichlor or trichlor raises free chlorine to your target ppm. Gallons or litres. Guidance — follow the label.
- Pool salt calculatorHow much salt to add to a saltwater pool: pounds, kilograms and 40 lb or 25 kg bags to raise salt from your reading to 3,200 ppm or your chlorinator’s target.
- Pool & pond evaporation calculatorEstimate how much water a pool or pond loses to evaporation per day, week and month from its surface area and daily level drop. Gallons or litres.