How to use the pool chemical calculator
- Enter your pool volume in gallons or litres (use the Pool Volume Calculator if you don’t know it).
- Enter your latest test results: free chlorine, pH, total alkalinity, stabilizer (CYA), calcium hardness and salt if you have a salt system.
- Check the targets. The defaults suit most plaster and vinyl pools; adjust them to your equipment maker’s advice.
- Pick the products you actually have. The calculator gives a step-by-step plan in the right order.
Recommended pool water levels
| Test | Typical target | Notes |
|---|---|---|
| Free chlorine (FC) | At least 7.5% of CYA | e.g. 3–5 ppm at CYA 40 |
| pH | 7.4–7.6 | 7.2–7.8 is acceptable |
| Total alkalinity (TA) | 60–90 ppm | Lower TA keeps pH steadier with liquid chlorine |
| Stabilizer (CYA) | 30–50 ppm | 60–80 ppm with a salt chlorine generator |
| Calcium hardness (CH) | 250–350 ppm | Plaster pools; 50–150 ppm is fine for vinyl and fibreglass |
| Salt | 3,000–3,500 ppm | Check your salt cell’s manual |
The maths behind the doses
1 ppm = 1 mg per litre of pool water Chlorine (g of available Cl) = ΔFC × litres ÷ 1,000 Baking soda (g) = ΔTA ÷ 50,043 × 84.0 × litres Stabilizer (g) = ΔCYA × litres ÷ 1,000 Calcium chloride = ΔCH ÷ 100.09 × 110.98 × litres ÷ 1,000 ÷ purity Salt (g) = Δsalt × litres ÷ 1,000 Drain % = (1 − target ÷ current) × 100
For pH, the calculator models the carbonate and cyanurate buffers in your water: it works out how much alkalinity must be neutralised (by acid) or added (by soda ash) to move the pH to your target. Our results match PoolMath-style calculations within a few percent — for example about 10 fl oz of 31.45% acid to move a 12,000 gallon pool from pH 8.0 to 7.6 with TA 80. Real pools also contain borates and other buffers, so always add a little less, circulate and retest.
Quick reference per 10,000 US gallons
| Change | Product | Amount |
|---|---|---|
| FC +1 ppm | Liquid chlorine 12.5% | 10.2 fl oz |
| FC +1 ppm | Bleach 6% | 20.7 fl oz |
| FC +1 ppm | Cal-hypo 65% | 2.05 oz (weight) |
| TA +10 ppm | Baking soda | 1.4 lb |
| CYA +10 ppm | Cyanuric acid | 13.4 oz (weight) |
| CH +10 ppm | Calcium chloride 77% | 1.2 lb |
| Salt +1,000 ppm | Pool salt | 83.5 lb |
Safety
Never mix pool chemicals together, especially chlorine and acid — it releases toxic chlorine gas. Add each one separately to the pool water with the pump running, acid diluted or poured slowly at a return. Store chlorine and acid apart, and wear goggles and gloves.