Pool Chlorine Calculator
Get the exact dose of chlorine to hit your target free chlorine (FC) level. Ideal FC for most pools: 2–4 ppm (1–3 ppm for CYA-free pools, higher for saltwater with stabilizer).
Quick reference: 6% bleach to raise FC by 1 ppm
- 10,000 gal → about 25 fl oz
- 15,000 gal → about 38 fl oz
- 20,000 gal → about 50 fl oz
How the math works
- Pounds of pure chlorine = (Target − Current) ppm × Gallons × 8.34 ÷ 1,000,000
- One gallon of 6% bleach ≈ 0.54 lb of available chlorine; 8.25% ≈ 0.74 lb; 12.5% ≈ 1.13 lb
- Dry products: divide pure chlorine lbs by the product strength (68% or 90%)
Shocking your pool
To clear algae or after heavy use, many pool owners raise FC to 10 ppm or higher (shock level depends on your cyanuric acid level — the higher the CYA, the higher the shock level). Set your target in the calculator to 10 ppm to get a shock dose. Add in the evening with the pump running, and don't swim until FC falls back to the safe range.
Frequently asked questions
Can I use regular Clorox bleach in my pool?
Yes — plain, unscented 6–8.25% bleach is chemically identical to "pool bleach" and often cheaper at big-box stores. Avoid splash-less or scented varieties.
How long after adding chlorine can I swim?
For normal dosing, once the water is mixed (15–30 minutes with the pump on) and FC is at a normal level. After a shock dose, wait until FC drops below the safe limit for your CYA level — usually overnight.
Why does my chlorine disappear every day?
Sunlight burns off unstabilized chlorine fast. If your cyanuric acid (CYA) is near zero, add stabilizer. High water temperature and heavy bather load also increase daily chlorine demand.