Pool Chlorine Calculator
Enter your pool volume and current and target free chlorine to get the exact amount of chlorine to add, for liquid chlorine, bleach, cal-hypo, or dichlor. The dosing is derived from the standard mass balance and cross-checked against established pool-chemistry sources.
Add to raise FC by 4 ppm
61.4 fl oz
about 1.9 quarts
of Liquid chlorine 12.5%
Adds no CYA or calcium. The cleanest way to raise FC.
Not sure what target FC to use?
The right free chlorine level depends on your cyanuric acid (stabilizer). Enter your CYA to see the minimum, target, and shock levels from the widely used FC/CYA chart.
Add chlorine with the pump running, and ideally in the evening so the sun does not burn it off before it works. Add in stages, circulate, and retest before adding more. Never mix different chlorine products together, and never combine cal-hypo and liquid chlorine in the same bucket.
Free chlorine and stabilizer go together
The single most common chlorine mistake is treating free chlorine as a fixed target. It is not. Cyanuric acid protects chlorine from sunlight but also weakens it, so a pool with high CYA needs more free chlorine to stay sanitary, and a pool with low CYA needs less. Know your CYA first, then set your FC target from it. If you need to raise CYA, the stabilizer calculator handles that, and the volume calculator gives you the gallons every dose depends on.
Frequently asked questions
How much chlorine do I add to my pool?
It depends on your pool volume, how far the free chlorine needs to rise, and which product you use. As a reference point, one gallon of 10 percent liquid chlorine raises 10,000 gallons by about 10 ppm. This calculator works out the exact amount for liquid chlorine, bleach, cal-hypo, or dichlor at your volume.
What should my free chlorine level be?
There is no single safe number. The right free chlorine depends on your cyanuric acid (stabilizer). A common guide is to keep FC around 11 to 12 percent of your CYA as a target, with a minimum near 7.5 percent. Enter your CYA in the helper above to see the min, target, and shock levels.
Which chlorine is best to add?
Liquid chlorine or plain bleach is the cleanest way to raise free chlorine because it adds no cyanuric acid or calcium. Cal-hypo adds calcium hardness, and dichlor adds cyanuric acid, so repeated use of those slowly drives those levels up. For routine dosing most people use liquid chlorine.
How much liquid chlorine raises 1 ppm in 10,000 gallons?
About 10.2 fluid ounces of 12.5 percent liquid chlorine, or about 12.8 fluid ounces of 10 percent. Plain 8.25 percent bleach takes about 15.5 fluid ounces. The calculator scales these to your exact volume and target.
Can I add too much chlorine?
Yes. Overshooting wastes product and can make the water harsh, and very high levels can damage equipment over time. It is not easily reversed, so add in stages, run the pump, and retest before topping up. A chlorine neutralizer (sodium thiosulfate) can bring down a large overshoot if needed.
When is the best time to add chlorine?
In the evening. Sunlight breaks down unstabilized chlorine quickly, so dosing at night lets it work and circulate before the next day. Always add with the pump running so it mixes through the pool.
Dosing based on the standard mass balance (8.345e-6 lb active chlorine per ppm per gallon), anchored on the Trouble Free Pool reference that 1 gallon of 10% liquid chlorine raises 10,000 gallons by 10 ppm, and cross-checked against Swim University, Sutro, and the Indiana Department of Health pool chemical guidance. Always follow your product label and retest.