Chlorine Calculator
Raise your pool's free chlorine to a target ppm with liquid, cal-hypo or dichlor chlorine.
Chlorine Dose
Not sure whether salt or traditional chlorine is right for your pool? Take the Salt or Chlorine Finder.
Take the quizHow chlorine dosing is calculated
Different chlorine products have different available-chlorine concentrations, so the same 1 ppm free-chlorine increase needs a different amount depending on which product you're using. This calculator uses 12.5% liquid chlorine as the reference rate (10 fl oz per 10,000 gallons per 1 ppm) and scales the other product types relative to their concentration.
10% liquid chlorine needs proportionally more volume than 12.5% (12.5 fl oz per 10,000 gallons per 1 ppm); 65% and 73% cal-hypo need much smaller weights since they're far more concentrated (about 2 oz and 1.78 oz per 10,000 gallons per 1 ppm respectively); 56% dichlor sits in between at about 2.5 oz.
Dichlor also adds cyanuric acid (stabilizer) to your water with every dose, which is useful up to a point but can build up over a season with frequent dichlor use -- if you use dichlor as your primary chlorine source, keep an eye on your cyanuric acid level too.
Where these numbers come from
The formulas and default values in this calculator are based on:
- standard rule-of-thumb chlorine dosing rates published by pool-supply retailers and chemical manufacturers, scaled by product concentration (12.5% liquid chlorine as reference at ~10 fl oz per 10,000 gal per 1 ppm FC)
These are planning estimates. Test your actual water, follow product labels, and check your equipment manufacturer's guidance before you buy or dose chemicals.
Frequently asked questions
Which chlorine type is cheapest to dose with?
Cost per ppm varies by local pricing more than by chemistry -- cal-hypo and liquid chlorine are usually the most cost-effective per gallon of pool treated, while dichlor tends to cost more per ppm but is convenient for smaller doses and spas. Compare your local prices per pound or per gallon of product.
Is unstabilized or stabilized chlorine better?
Stabilized chlorine (like dichlor or trichlor) contains cyanuric acid, which protects chlorine from breaking down in sunlight -- useful outdoors, but it accumulates over time. Unstabilized chlorine (liquid chlorine, cal-hypo) breaks down faster in the sun but doesn't add to cyanuric acid buildup, which is why many pools use a mix of both.
How often should I dose chlorine?
Most pools need a small daily or every-other-day chlorine addition to maintain a steady 1-3 ppm free chlorine range, on top of periodic shocking. An automatic chlorinator or salt system reduces how often you need to dose manually.
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