One water test, every dose
Balancing a pool means getting several numbers into range at the same time: free chlorine, pH, total alkalinity, calcium hardness, stabilizer (cyanuric acid) and, for saltwater pools, salt. Each has its own chemical and its own dose per gallon or litre. This calculator takes the results from your test kit or pool shop printout, compares them with your targets, and lists what to add and in what order. Leave a target blank, or equal to the current reading, to skip that chemical.
Recommended ranges
| Test | Recommended | Source |
|---|---|---|
| Free chlorine | At least 1 ppm (pools), at least 2 ppm with stabilizer, at least 3 ppm (hot tubs) | CDC |
| pH | 7.0–7.8; 7.2–7.6 recommended in Australia | CDC; AS 3633 via SPASA |
| Total alkalinity | 60–200 ppm; about 100–120 ppm typical target | AS 3633 via SPASA |
| Calcium hardness | 80–500 ppm | AS 3633 via SPASA |
| Cyanuric acid | Outdoor pools only, commonly about 30–50 ppm; none in hot tubs | CDC (no CYA in hot tubs); industry practice |
| Salt | As your chlorinator manual specifies | Manufacturer |
The order to add chemicals
- Total alkalinity first, because it buffers pH. Baking soda raises it; acid with aeration lowers it.
- pH next. pH dosing depends on alkalinity and the product, so this calculator does not give a single number; add acid (to lower) or soda ash (to raise) in small label doses and retest. With alkalinity right, pH usually needs only small corrections.
- Calcium hardness, pre-dissolved, in portions.
- Stabilizer, slowly, in a sock in front of a return jet.
- Chlorine last, in the evening, once pH is in range (chlorine works best between pH 7.2 and 7.8).
- Salt, with the chlorinator switched off until it dissolves.
Run the pump throughout, add one chemical at a time, and leave several hours between chemicals. Never mix chemicals together, especially chlorine and acid.
Worked example
A 20,000-gallon pool tests: free chlorine 1.5, pH 7.8, alkalinity 80, calcium hardness 180, stabilizer 30. Targets: chlorine 5, alkalinity 100, hardness 250, stabilizer 40.
- Alkalinity +20 ppm: 5.6 lb (2.54 kg) of baking soda.
- pH 7.8 is at the top of the range: add a small dose of acid and retest.
- Calcium hardness +70 ppm: 16.8 lb (7.63 kg) of 77% calcium chloride, in two or three portions.
- Stabilizer +10 ppm: 1.67 lb (757 g) of cyanuric acid.
- Chlorine +3.5 ppm: 71.7 fl oz (2.12 L) of 12.5% liquid chlorine.
If the same pool were a salt pool reading 2,800 ppm with a 3,200 ppm target, it would also need 66.8 lb (30.3 kg) of salt.
Tips for accurate results
- Get the volume right. Every dose scales with it; use the pool volume calculator.
- Use a good test kit. Drop-count (titration) kits for chlorine, alkalinity and hardness are more precise than strips.
- Check the strength on your label. Liquid chlorine and acid come in different strengths; choose the matching product.
- Check scale and corrosion risk with the pool water balance (LSI) calculator once the numbers are close.
Common mistakes
- Adding everything at once. Chemicals react with each other; large doses can cloud the water.
- Shocking with high pH. At pH above 8.0 chlorine is much less effective, according to the CDC.
- Forgetting what products add. Cal-hypo adds calcium; dichlor and trichlor add stabilizer. The chlorine calculator shows how much.
Estimates for general information. Always read and follow the product label, and keep chemicals away from children.
Quick reference: doses per 10,000 gallons (37,854 L)
| To change | By | Add |
|---|---|---|
| Free chlorine | +1 ppm | 10.2 fl oz (303 mL) liquid chlorine 12.5% |
| Free chlorine | +1 ppm | 2.1 oz (58 g) cal-hypo 65% |
| Total alkalinity | +10 ppm | 1.4 lb (635 g) baking soda |
| Total alkalinity | −10 ppm | 25.6 fl oz (756 mL) muriatic acid 31.45% |
| Calcium hardness | +10 ppm | 1.2 lb (545 g) calcium chloride 77% |
| Cyanuric acid | +10 ppm | 13.4 oz (379 g) stabilizer |
| Salt | +100 ppm | 8.35 lb (3.79 kg) pool salt |
Scale these by your volume: a 20,000-gallon pool needs twice as much, a 5,000-gallon pool half as much. The calculator above does this for every chemical at once.
Frequently asked questions
What order should I add pool chemicals?
Alkalinity first, then pH, then calcium hardness, then stabilizer, then chlorine, then salt if you have a salt chlorinator. Add one at a time with the pump running and never mix chemicals.
What are the ideal pool chemical levels?
CDC: free chlorine at least 1 ppm (2 ppm with stabilizer), pH 7.0–7.8. AS 3633 via SPASA: alkalinity 60–200 ppm (about 100–120 typical), calcium hardness 80–500 ppm.
How much chlorine do I add to a 20,000 gallon pool?
To raise free chlorine by 3.5 ppm, about 72 fl oz (2.1 L) of 12.5% liquid chlorine. Each 1 ppm needs about 20.5 fl oz in 20,000 gallons.
Can I use this pool chemical calculator in litres?
Yes. Choose litres as the volume unit; doses are shown in both US units and metric.
How much baking soda for a 10,000 gallon pool?
About 1.4 lb (635 g) raises total alkalinity by 10 ppm.
Sources
- CDC: Home pool and hot tub water treatment and testing.
- SPASA Australia: Water balance (AS 3633 ranges).
- Doses calculated from molar masses and typical product strengths; see each single-chemical calculator for details.
Last reviewed 28 October 2026. Results are estimates; see our disclaimer.