Pool chlorine calculator
Estimate how much chlorine raises free chlorine (FC) from your test reading to the target. This is guidance for planning: always follow the product label and retest.
How the dose is worked out
One ppm is one milligram per litre, so raising a pool by 1 ppm takes litres ÷ 1,000 grams of available chlorine. Divide by the product’s strength to get the product amount. For 10,000 US gallons (37,854 L), +1 ppm needs 37.9 g of chlorine:
| Product | Strength | Per 10,000 US gal per 1 ppm |
|---|---|---|
| Liquid chlorine (sodium hypochlorite) | 12.5% | 10.2 fl oz (303 mL) |
| Plain household bleach | 6% | 21.3 fl oz (631 mL) |
| Cal-hypo (calcium hypochlorite) | 65% | 2.1 oz (58 g) |
| Dichlor granules | 56% | 2.4 oz (68 g) |
| Trichlor (tablets or granules) | 90% | 1.5 oz (42 g) |
These match the state health department and pool-industry dosing charts (about 10.7 fl oz of 12% liquid chlorine and 2 oz of 65% cal-hypo per 10,000 gallons per ppm). Liquid strengths are "trade %", grams of chlorine per 100 mL; liquid chlorine loses strength over weeks in the heat, so old jugs dose weaker.
Safety
- Never mix chlorine products with each other or with acid — dangerous gas can form.
- Add chemicals to water, never water to chemicals. Dose with the pump running and nobody in the pool.
- Stabilized products (dichlor, trichlor) also add cyanuric acid; their long-term use raises CYA.
Read the pool chlorine basics guide for target levels, pH and stabilizer.
Questions
How much liquid chlorine do I add to raise free chlorine 1 ppm?
About 10.2 fl oz of 12.5% liquid chlorine per 10,000 US gallons (or 21 fl oz of 6% bleach). Scale with your pool size and the ppm you need, then follow the product label.
What should free chlorine be in a pool?
At least 1 ppm at all times is a common public-health minimum; many residential pools aim for 2–4 ppm, and more when stabilizer (CYA) is high.
Is household bleach the same as pool chlorine?
Plain unscented bleach is sodium hypochlorite like liquid pool chlorine, just weaker (often 5–8%). Avoid scented, splash-less or "with additives" bleach.