Chlorine Tablets Calculator Australia
Tablet labels give a starting rate. Your real rate depends on sun, swimmers and rain, which change how much chlorine the pool loses each week. The chart shows what one tablet adds to your pool, so you can match the tablet count to the loss you measure.
Work out how many tablets you need
- Test free chlorine, then test again a week later with the same tablets in place and no other chlorine added. The drop is your weekly loss.
- Tablets needed per week ≈ weekly loss in ppm ÷ ppm added by one tablet (from the chart). Round down, then adjust after the next test.
- Keep free chlorine in range (about 1–3 ppm in most Australian guidance) and stabiliser at 30 ppm or less for ideal control, never above 50 ppm. Tablets push stabiliser up every week, so you cannot rely on them indefinitely.
- Tablets keep a level steady. They dissolve too slowly to recover a green or cloudy pool; use a shock dose for that.
Australian dose chart
The chart assumes one 200 g trichlor tablet with about 90% available chlorine, fully dissolved: roughly 180 g of chlorine spread through the pool. Left column is the chlorine rise (ppm), right column is the stabiliser (CYA) added alongside it, at roughly 0.6 ppm CYA for every 1 ppm of chlorine. Brands differ, so check the strength on your tub.
| Pool volume | Free chlorine added by one 200 g tablet | Stabiliser (CYA) added at the same time |
|---|---|---|
| 30,000 L | ≈ 6.0 ppm | ≈ 3.6 ppm |
| 50,000 L | ≈ 3.6 ppm | ≈ 2.2 ppm |
| 75,000 L | ≈ 2.4 ppm | ≈ 1.4 ppm |
| 100,000 L | ≈ 1.8 ppm | ≈ 1.1 ppm |
How to dose without overshooting
- Confirm your pool volume in litres. Every tablet count below reads off that volume.
- Test free chlorine, pH and stabiliser (CYA) before the first tablet of the week and write the readings down.
- Start with the rate on the product label, using a floating dispenser or inline feeder as the label directs. Do not leave tablets sitting in the pump strainer basket, and do not let tablets sit in the skimmer unless the pump runs the whole time they are in it.
- Retest after seven days. If free chlorine fell below your target, add a tablet. If it is above the target, take one away.
- Test stabiliser every two weeks in summer. When it reaches about 50 ppm, stop using stabilised tablets and top up with liquid chlorine instead.
Want the numbers worked out for you? Enter your pool volume and test results in our pool chemical calculator to see every dose in one check.
Safety and system checks
- One 200 g tablet suits pools of about 30,000 L and up. In a smaller pool it overshoots badly: in 10,000 L a single tablet adds about 18 ppm of chlorine and 11 ppm of stabiliser. Use liquid chlorine, or mini tablets, in pools under about 30,000 L.
- Never mix tablets with liquid chlorine, calcium hypochlorite, acid or any other pool chemical, and never store them near other chemicals. Mixing can release toxic gas.
- Trichlor tablets are acidic. Over weeks they lower pH and total alkalinity, so test both and fix low alkalinity with the bicarb dose in the alkalinity calculator.
- Stabiliser breaks down very slowly, so the practical way to lower it is draining and refilling part of the pool. Rain and top-ups barely dilute it.
- Do not use stabilised tablets in a Naked freshwater system. If you run a salt chlorinator, check the chlorinator maker’s instructions before adding tablets.