calcs.homes
calcs.homes
Enter your current and target free chlorine level and pick your product to find exactly how much to add.
Estimate only — add at dusk to reduce UV loss, and retest after circulating.
We subtract current free chlorine from your target reading, divide pool volume by 10,000 gallons, and multiply by the constant for your chosen product: 10.1 fl oz for 10% liquid chlorine, 8.1 fl oz for 12.5% liquid chlorine, or 2 oz by weight for 65% cal-hypo granular, all per 10,000 gallons per 1 ppm. If current chlorine already meets or beats target, the dose comes back as zero rather than negative.
Each constant scales with the product's available-chlorine concentration, so a weaker 10% liquid needs noticeably more volume than a stronger 12.5% liquid or a concentrated granular to deliver the same ppm increase. Keeping free chlorine in the 1-3 ppm range (higher with elevated stabilizer) is the standard sanitizing target — too low and bacteria or algae can take hold, too high and it can irritate skin and eyes.
1-3 ppm for most pools, though pools with higher stabilizer (CYA) levels may need 3-5 ppm to sanitize as effectively — check the Free Chlorine / CYA ratio if algae keeps coming back.
Different chlorine products carry different concentrations of available chlorine — a weaker 10% liquid needs more volume than a stronger 12.5% liquid to deliver the same ppm boost.