Chlorine dosing is all "per X gallons," so the first step is always knowing your pool's volume. Once you have that, the amount to add is simple math — here are the rules of thumb.
The liquid-chlorine rule
About 10.7 fl oz of 12.5% liquid chlorine raises 10,000 gallons by 1 ppm of free chlorine. So a 15,000-gallon pool raised 3 ppm needs roughly 48 fl oz (about 6 cups). The pool chlorine calculator scales it to your gallons, target, and product strength.
What free chlorine level to aim for
- Normal: keep free chlorine around 1–3 ppm for everyday swimming.
- Shock: raise it to about 10 ppm (or follow the shock product's label) to clear algae, cloudiness, or after heavy use.
Bleach vs pool chlorine
Household bleach is usually ~6% sodium hypochlorite — about half the strength of 12.5% pool chlorine — so you'll need roughly double the volume. In the calculator, just set the strength field to your product's percentage.
Best practices
- Add chlorine in the evening with the pump running — midday sun burns off unstabilized chlorine within hours.
- Start conservative and retest. It's easy to add more; you can't easily take it out.
- Keep cyanuric acid (stabilizer) in range so your chlorine lasts, and never mix chlorine products together.
Not sure of your volume? Run the rectangular or round pool calculator first — every dose depends on it.