How to use the pool chlorine calculator
- Enter the pool volume in gallons. Use the pool volume calculator if you are not sure.
- Test the water and enter the current free chlorine (FC) reading.
- Enter the target. Many pools are kept around 2 to 4 ppm free chlorine. Outdoor pools with stabilizer (CYA) need more: a common rule is free chlorine of at least 7.5% of the CYA level.
- Pick the product and its strength from the label (available chlorine).
The pool chlorine formula
Liquid (gallons) = pounds of chlorine ÷ (strength × 8.345)
Granules (pounds) = pounds of chlorine ÷ strength
Liquid chlorine strengths are given as trade percent (weight of chlorine per volume), so a gallon of 12.5% liquid chlorine holds about 1.04 lb of available chlorine.
How much to raise 1 ppm in 10,000 gallons
| Product | Amount for +1 ppm per 10,000 gal |
|---|---|
| Liquid chlorine 12.5% | 10.2 fl oz |
| Liquid chlorine 10% | 12.8 fl oz |
| Bleach 8.25% | 15.5 fl oz |
| Bleach 6% | 21.3 fl oz |
| Cal-hypo 65% | 2.05 oz by weight |
| Dichlor 56% | 2.38 oz by weight |
| Trichlor 90% | 1.48 oz by weight |
Scale it: twice the pool size or twice the ppm takes twice the amount.
Worked example
A 15,000 gallon pool reads 1 ppm and you want 4 ppm, a rise of 3 ppm. 3 × 15,000 × 8.34 ÷ 1,000,000 = 0.375 lb of chlorine. With 12.5% liquid chlorine that is 0.375 ÷ (0.125 × 8.345) = 0.36 gallons, or about 46 fl oz. The same rise takes about 96 fl oz of 6% bleach or about 9.2 oz of 65% cal-hypo.
Liquid, granules or tablets?
- Liquid chlorine and bleach add nothing but chlorine and a little salt. Use plain, unscented bleach without additives.
- Cal-hypo also adds calcium hardness. Pre-dissolve it in a bucket of water so it does not bleach a vinyl liner.
- Dichlor and trichlor add stabilizer (CYA): about 0.9 ppm and 0.6 ppm of CYA for every 1 ppm of chlorine. Over a season that builds up, so many pool owners switch to liquid once CYA is high enough.
Running a salt water pool? Keep the salt in range with the pool salt calculator.
Frequently asked questions
How much liquid chlorine do I add to my pool?
About 10.2 fl oz of 12.5% liquid chlorine raises free chlorine by 1 ppm in 10,000 gallons. For a 15,000 gallon pool going from 1 to 4 ppm, that is about 46 fl oz.
How much bleach do I put in my pool?
About 21 fl oz of 6% bleach raises 10,000 gallons by 1 ppm. Use plain, unscented bleach with no additives.
What should free chlorine be in a pool?
Many pools are kept at about 2 to 4 ppm. Outdoor pools with stabilizer need more; a common guide is at least 7.5% of the cyanuric acid (CYA) level.
How much shock do I need for my pool?
About 2 oz of 65% cal-hypo raises 10,000 gallons by 1 ppm, so raising a 15,000 gallon pool by 10 ppm takes about 1.9 lb. Follow the product label for shock levels.
Why does my chlorine drop so fast?
Sunlight breaks chlorine down quickly without enough stabilizer (CYA). Algae, swimmers and warm water also use it up. Test daily and keep CYA in the range your test kit recommends.
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Last updated October 2026.