Pool Chlorine Dose Calculator
Calculate exact chlorine dose to raise pool free chlorine from current ppm to target.
Supports liquid bleach, granular cal-hypo, and dichlor.
The math for raising free chlorine in a pool is straightforward once you know the strength of what you are pouring in. The same one ppm of free chlorine costs different amounts of liquid, granular, or tablet depending on the product. People constantly overdose because they assume “shock is shock.”
For 10,000 gallons, raising free chlorine by 1 ppm needs roughly:
- Liquid bleach (10% sodium hypochlorite, pool-strength): 10.5 fl oz
- Liquid bleach (8.25% sodium hypochlorite, household): 12.8 fl oz
- Cal-hypo granular (65% calcium hypochlorite): 1.3 oz by weight
- Dichlor granular (56% available chlorine): 1.5 oz by weight
- Trichlor tablet (90% available chlorine): 0.9 oz by weight
Multiply linearly with both pool size and the ppm you want to raise. So a 20,000-gallon pool that reads 1 ppm and you want at 4 ppm needs three ppm of correction across double the volume — six times the per-10k-per-ppm number.
A few practical notes that keep people out of trouble. Always test before you dose. The single biggest cause of green pools is people dosing on schedule without testing first; the single biggest cause of bleached liners is the opposite. A reliable test kit (Taylor K-2006 or any decent DPD kit) takes 90 seconds and saves you hundreds of dollars over a season.
Cyanuric acid changes the math. If your CYA is over 50 ppm, the effective chlorine is much lower than the test number suggests, and the standard advice is to keep free chlorine at roughly 7.5% of CYA. Trichlor and dichlor both add CYA every time you use them, which is why long-time pool owners stop using them and switch to liquid for routine dosing.
Pour liquid in front of a return jet, with the pump running, never near skimmers. Granular goes through a brush — pre-dissolve it in a bucket of pool water if your pool has a vinyl liner, since direct cal-hypo on a liner can bleach it permanently. And do not mix two chlorine types in the same bucket. Trichlor and cal-hypo, when combined dry, can react vigorously enough to start a fire. This sounds like internet hyperbole, and it is not.