Pool Chlorine Calculator
Not sure how much chlorine to add? Enter your pool volume, your current free chlorine reading, and the level you're aiming for. The calculator shows how much liquid chlorine or cal-hypo shock you need — whether you're topping up daily chlorine or shocking the pool.
A stabilized pool is usually kept around 2–4 ppm free chlorine. To “shock,” you temporarily raise it to about 10–12 ppm (or 10× your combined chlorine reading). Always add chlorine with the pump running, and never mix different chlorine products together.
Enter your pool volume and chlorine levels.
How the calculation works
Chlorine products differ in strength, so the dose depends on which one you use. The calculator scales a known reference dose to your pool size and the ppm increase you want.
- Liquid chlorine (12.5%): about 1 gallon raises 10,000 gallons of water by roughly 10.5 ppm free chlorine.
- Cal-hypo granular (73%): about 1 lb raises 10,000 gallons by roughly 8.75 ppm free chlorine.
A few tips: always add chlorine with the pump running so it disperses, and add liquid chlorine in the evening so the sun doesn't burn it off before it works. Never mix different chlorine products together. After shocking, wait until free chlorine falls back to about 5 ppm or lower before swimming. Not sure of your volume? Use the Pool Volume Calculator first, and check all your levels with the Chemistry Calculator.