How much chemical do I add to my pool?
Every pool chemical dose comes down to three numbers: the pool's volume, how far you want to move a reading, and how much of the product it takes to move that reading 1 ppm in 10,000 gallons.
Amount = dose per 1 ppm per 10,000 gal × (target − current) × gallons ÷ 10,000
A 15,000 gallon pool with free chlorine at 1 ppm, target 4 ppm, using 12.5% liquid chlorine: 10.24 fl oz × 3 × 1.5 = 46.1 fl oz, a little over a third of a gallon.
If you don't know your volume, work it out first with the pool volume calculator. A volume that's off by 20% makes every dose off by 20%.
Doses per 10,000 gallons
| Chemical | Changes | Amount per 10,000 gal |
|---|---|---|
| Liquid chlorine, 10% | Free chlorine +1 ppm | 12.8 fl oz |
| Liquid chlorine, 12.5% | Free chlorine +1 ppm | 10.2 fl oz |
| Cal-hypo, 65% | Free chlorine +1 ppm | 2.1 oz by weight |
| Cal-hypo, 73% | Free chlorine +1 ppm | 1.8 oz by weight |
| Sodium bicarbonate | Total alkalinity +10 ppm | 1.4 lb |
| Muriatic acid, 31.45% | Total alkalinity −10 ppm | 25.6 fl oz |
| Cyanuric acid | Stabilizer +10 ppm | 13.4 oz by weight |
| Calcium chloride, 77% | Calcium hardness +10 ppm | 1.2 lb |
| Calcium chloride, 94–97% | Calcium hardness +10 ppm | 15.5 oz by weight |
These figures are worked out from each product's strength, assuming full-strength product. Liquid chlorine loses strength as it sits, especially in heat, so an old jug raises chlorine less than the chart says. Your product's label may give slightly different numbers. Follow the label.
Safety first
Pool chemicals are dangerous when mishandled. Read and follow the label on every product. Add one chemical at a time, with the pump running, and let the water circulate before adding the next. Never mix chemicals together, and never put chlorine and acid in the same bucket or near each other: together they release chlorine gas. When diluting acid, add acid to water, never water to acid. Wear eye protection and gloves, and store products apart, dry and out of reach of children.
For a big change, add part of the dose, circulate for a few hours and retest before adding the rest. This calculator gives a starting point, not a guarantee. Your test results are what count.
Typical target ranges
| Reading | Typical range |
|---|---|
| Free chlorine | 1–4 ppm |
| pH | 7.2–7.8 |
| Total alkalinity | 60–120 ppm |
| Calcium hardness | 200–400 ppm |
| Cyanuric acid (outdoor pools) | 30–50 ppm |
Ranges differ between test kit makers, pool surfaces and local health codes. Stabilized pools need more free chlorine as cyanuric acid rises, so use the targets your test kit or pool professional recommends.
Lowering pH and alkalinity
Muriatic acid lowers both pH and total alkalinity. The calculator doses acid by alkalinity, because that relationship is predictable. How far a dose moves pH depends on your alkalinity and other factors, so to lower pH alone, add a small measured amount, circulate, retest and repeat. Many acid labels and test kits include a pH dosing chart. Lower alkalinity in stages rather than all at once, and don't let pH fall below the bottom of the range.
Above ground pool chemicals
The math is the same for an above ground pool. These pools are often smaller, so doses are small and easy to overshoot. A 24 ft round pool with 4 ft of water holds about 13,500 gallons. Measure liquids with a marked cup, not by eye.
Stabilizer and calcium
Cyanuric acid protects chlorine from sunlight, but it builds up and doesn't break down in normal use. The usual way to lower it, or to lower calcium hardness, is to drain part of the water and refill. Add stabilizer slowly: it dissolves over days, so wait about a week before retesting it.
Questions
How much liquid chlorine do I add to raise chlorine 1 ppm?
About 12.8 fl oz of 10% liquid chlorine or 10.2 fl oz of 12.5% per 10,000 gallons, at full strength. Older chlorine has lost strength and needs more. Follow the label.
How much baking soda raises alkalinity 10 ppm?
About 1.4 lb of sodium bicarbonate per 10,000 gallons. For a 15,000 gallon pool going from 70 to 100 ppm, that's about 6.3 lb.
How much muriatic acid lowers alkalinity?
About 25.6 fl oz of 31.45% muriatic acid per 10,000 gallons lowers total alkalinity by about 10 ppm. Add it in stages and retest.
Can I add pool chemicals at the same time?
No. Add one chemical at a time with the pump running, let it circulate, then add the next. Never mix chemicals together, especially chlorine and acid.