Pool chlorine and chemical calculator
Tell us the size of your pool and what the water looks like. The calculator shows how much chlorine to add, in spoons and cups, and what to do next. Works with any brand, no test kit needed.
Result
Estimate. Check the product label (if it differs, follow the label), add one product at a time and test again before anyone swims.
Safety
- Never mix different products, dry or dissolved. Add one at a time, with a gap in between.
- Dissolve granules in a bucket of pool water before adding them. Always add the product to water, never water to the product.
- Wear gloves and eye protection when handling acid and chlorine. Store away from children and out of the sun.
- These are estimates for home use. Always follow the manufacturer's label and test again after dosing.
In case of an accident: call emergency services (000 in Australia, 111 in New Zealand, 999 in the UK) or the Poisons Information Centre (13 11 26 in Australia), and bring the product container.
Ideal water levels
| Parameter | Ideal range |
|---|---|
| Free chlorine | 1 to 3 ppm |
| pH | 7.2 to 7.6 |
| Total alkalinity | 80 to 120 ppm |
| Stabiliser (CYA), outdoor pool | 30 to 50 ppm |
| Salt (chlorinator) | as specified by the chlorinator maker |
Why the order matters
Alkalinity holds the pH steady, and pH controls how well chlorine works: at high pH, chlorine loses much of its strength. So the order is always alkalinity, then pH, then chlorine.
How much chlorine by pool size
Frequently asked questions
How much chlorine should I add per day?
With normal use, pools usually lose 1 to 2 ppm a day, depending on sun, heat and swimmers. Test the free chlorine and use the calculator to top up to about 2 ppm.
Can I use household bleach in the pool?
Yes, as long as it's plain bleach with no scent or additives. It's weaker than pool chlorine (often 4–5%), so you need more of it. Choose "Household bleach" in the calculator and check the % on the label.
Why does the chlorine disappear so fast?
Sunlight destroys unstabilised chlorine. In an outdoor pool, keep stabiliser (CYA) between 30 and 50 ppm. Leaves, dirt and algae also use up chlorine.