Pool Volume & Chemical Calculator
Enter the pool shape and depths to get the volume in cubic metres, litres and US gallons, then the salt, shock chlorine and baking soda to add, plus the filter turnover time.
Every pool chemical dose is a concentration, so the first number you need is the volume. Pick the shape, measure the depths, and the page returns litres, gallons, the salt for start-up, the shock dose and the filter turnover time.
The pool
Measure in metres. If the floor slopes, use the shallow and deep ends; the average depth is applied automatically.
Volume
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Litres
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US gallons
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Salt to start
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Shock chlorine
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Baking soda (+10 ppm TA)
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One turnover
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How this was worked out
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Common pool sizes
| Pool | Volume | Salt |
|---|---|---|
| 6 × 3 m, 1.2 m | 21.6 m³ | 64.8 kg |
| 8 × 4 m, 1.5 m | 48.0 m³ | 144.0 kg |
| 10 × 5 m, 1.5 m | 75.0 m³ | 225.0 kg |
| 12 × 6 m, 1.6 m | 115.2 m³ | 345.6 kg |
| Round, 4 m dia, 1.2 m | 15.1 m³ | 45.2 kg |
Four rules for dosing
- Salt pools run at about 3,000 ppm, which is 3 kg per cubic metre. Add it with the pump running and brush until it dissolves.
- A shock dose is about 10 g of chlorine per cubic metre. Raise it after heavy rain, a party or a heatwave.
- Baking soda at 17 g per cubic metre lifts total alkalinity by roughly 10 ppm. Adjust in steps and retest.
- Turn the whole volume over once a day. Runtime = volume ÷ filter flow, so a 48 m³ pool on an 8 m³/h pump needs about 6 hours.
Practical notes
- Measure the water depth, not the wall height. Most pools are filled 10–15 cm below the coping.
- For an irregular pool, split it into a rectangle plus a circle and add the two volumes.
- Add chemicals to water, never water to chemicals; run the pump for 24 hours after a shock dose.
- Test free chlorine, pH and alkalinity before every adjustment. Dosing blind is how pools go cloudy.
Three common mistakes
- Using the pool length × width as the volume. A 8 × 4 m pool varies from 38 to 58 m³ depending on depth.
- Dosing salt by the bag without checking the current level. Top up to 3,000 ppm, not from zero every time.
- Running the filter by habit instead of by turnover. Short runs leave the far end of the pool under-filtered.
Doses are starting points for a typical residential pool. Always read the product label, test the water, and keep chemicals away from children and pets.