Calculate swimming pool water volume from shape and dimensions, with approximate chlorine dosing guidance.
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Home & DIY
Calculating your swimming pool volume accurately is the foundation of safe water chemistry. Chlorine dosing, pH balancers, algaecides, and salt quantities for salt-chlorine systems all depend on knowing how many litres or gallons of water the pool holds. This pool volume calculator supports rectangular, oval, and round pool shapes with constant or variable depth.
A rectangular pool volume is Length × Width × Average Depth. For pools with a shallow end and a deep end, use the average depth: (shallow depth + deep depth) ÷ 2.
An oval pool approximates an ellipse. The formula is (π ÷ 4) × Length × Width × Average Depth, which is approximately 0.785 × Length × Width × Depth. A round pool uses the circular area: π × (Diameter ÷ 2)² × Depth.
The calculator provides approximate chlorine shock and weekly maintenance doses based on pool volume. An initial shock dose of around 20 g of stabilised chlorine granules per 1,000 litres is a common starting point for opening a pool at the start of the season.
Weekly maintenance typically requires around 5 g per 1,000 litres, adjusted based on actual test results and bather load. Always test pool water with a test kit before adding chemicals, and follow the product label. Chlorine requirements vary with temperature, UV exposure, and usage.
Pool volume calculations are estimates. Real pools have rounded corners, steps, and features that reduce true volume slightly from the calculated figure. Treat results as a starting point and adjust chemical doses based on water test results.
Vinyl liner pools may have irregular profiles where shallow and deep sections meet. In these cases, calculate each section separately and add the volumes.
Frequently asked questions
Measure the longest internal length and the widest internal width at water level. For depth, measure at the shallow end and at the deepest point. Use the average depth in the calculator for the most accurate result.
A typical UK garden pool measuring 6 m × 3 m with a constant depth of 1.35 m holds approximately 24,300 litres. A larger 10 m × 5 m pool with an average depth of 1.5 m holds around 75,000 litres.
Yes — a small rectangular paddling pool works the same way. For a round hot tub or spa, use the round shape option and enter the internal diameter and water depth, not the full shell height.
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