Pool Chlorine Dose Calculator
To raise pool free chlorine by a target amount you add a known mass of available chlorine. Since a gallon of water weighs 8.345 pounds and one ppm is one part per million by weight, the pure chlorine needed is volume times target ppm times 8.345, divided by a million. Real products are diluted, so you divide by the product's available-chlorine fraction to get the product weight to add. This calculator reports pounds, ounces, and (for liquid products) fluid ounces. Always confirm targets and maximums against CDC guidance and your local pool code.
Chlorine dose formula
Pure chlorine (lb) = volume * target ppm * 8.345 / 1,000,000
Product (lb) = pure chlorine / (available% / 100)
Product (oz) = product (lb) * 16
Liquid (fl oz) = product (lb) / density (lb per gal) * 128
A US gallon of water weighs 8.345 pounds, and 1 ppm is one part per million by weight. Dividing by the available-chlorine fraction accounts for products being diluted. The fluid-ounce line uses the liquid product density you enter.
Chlorine dosing context
- Calcium hypochlorite is roughly 65 to 73 percent available chlorine.
- Liquid sodium hypochlorite is often 10 to 12.5 percent available chlorine.
- One ppm is one milligram per kilogram, the same as one part per million by weight.
- Confirm target free chlorine and maximums against CDC guidance and local pool code.
- Add in steps, retest, follow product directions, and never mix chlorine products.
Pool chlorine: frequently asked questions
How much chlorine do I add to my pool?
The pure available chlorine needed equals the pool volume in gallons times the desired ppm rise times the weight of water (8.345 lb per gallon) divided by one million. Then divide by your product's available-chlorine fraction to get the product weight, because products are not pure. This calculator does that and shows pounds, ounces, and fluid ounces for liquid.
What is a ppm and how does it relate to weight?
One part per million (ppm) is one milligram of chlorine per kilogram of water, which by weight is the same as one part in a million. Since a US gallon of water weighs about 8.345 pounds, raising a pool by 1 ppm needs 8.345 millionths of a pound of pure available chlorine per gallon of water.
Why divide by the available-chlorine percent?
Chlorine products are not pure. Calcium hypochlorite is roughly 65 to 73 percent available chlorine, dichlor around 56 to 62 percent, and liquid sodium hypochlorite often 10 to 12.5 percent. You must add more product than the pure chlorine figure, so this calculator divides by the available-chlorine fraction printed on your product label.
What free chlorine level should a pool have?
The CDC recommends maintaining a free chlorine residual in line with public health guidance for the venue type, and your local health code sets the required range. This tool calculates the dose to reach a target you set; always confirm the target and maximums against CDC guidance and your local pool code.
Should I add chlorine all at once?
Follow the product directions. Many products are pre-dissolved or added to the skimmer or via a feeder, and adding too much at once can damage surfaces or be unsafe. Test the water, add in steps toward the target, retest, and never mix different chlorine products together.
Official sources
- U.S. Centers for Disease Control and Prevention: Healthy Swimming (disinfection).
- U.S. Environmental Protection Agency: EPA (pesticide-registered pool sanitizers).
Reviewed by the CalculatorHub team, edited by James Graham, 17 June 2026. See our methodology.