Pool chlorine and chemical calculator
How much chlorine, baking soda, calcium, stabilizer or salt to add, from the gallons and two test readings.
Amount to add
0 fl oz
How it works
pounds of the chemical = gallons x rise in ppm x 8.345 / 1,000,000 x compound factor / strength liquid chlorine (gallons) = pounds of chlorine / (strength x 8.345)
A part per million in a gallon of water weighs 8.345 millionths of a pound, so the dose follows straight from the gallons and the rise you want. Strength is the share of the product that does the work: 65% for most cal-hypo, 12.5% for pool-store liquid chlorine. Baking soda and calcium chloride are converted because test kits read alkalinity and hardness as calcium carbonate.
Amounts for 10,000 gallons
| Chemical | Raises | Amount |
|---|---|---|
| Liquid chlorine, 12.5% | Free chlorine +1 ppm | 10.2 fl oz |
| Cal-hypo shock, 65% | Free chlorine +1 ppm | 2.1 oz |
| Baking soda | Total alkalinity +10 ppm | 1.4 lb |
| Calcium chloride flake, 77% | Calcium hardness +10 ppm | 1.2 lb |
| Stabilizer (cyanuric acid) | CYA +10 ppm | 13.5 oz |
| Pool salt | Salt +100 ppm | 8.4 lb |
Common target ranges
| Reading | Range |
|---|---|
| Free chlorine | 1 to 4 ppm |
| pH | 7.2 to 7.8 |
| Total alkalinity | 80 to 120 ppm |
| Calcium hardness | 200 to 400 ppm |
| Stabilizer (CYA) | 30 to 50 ppm, higher for salt pools |
| Salt | As the cell's manual says, often 3,000 to 3,500 ppm |
Commercial and public pools follow the health department's limits. Add one chemical at a time with the pump running, and never mix two products together, least of all chlorine and acid or cal-hypo and trichlor.
Questions
- How much liquid chlorine raises a pool 1 ppm?
- About 10.2 fluid ounces of 12.5% liquid chlorine per 10,000 gallons, or 12.8 ounces of 10%.
- Why does my stabilizer keep climbing?
- Trichlor tablets and dichlor carry stabilizer with them. Each 1 ppm of chlorine from trichlor adds about 0.6 ppm of CYA, and from dichlor about 0.9 ppm.
- How do I lower a reading?
- Chlorine drops on its own in sunlight. Stabilizer, salt and calcium only come down when water is drained and replaced, and the calculator says how much.
- Can I add two chemicals at once?
- No. Add one, let the pump run, and wait before adding the next. Never mix chlorine with acid or cal-hypo with trichlor, even dry.
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