Pool shock calculator

How many 1 lb bags do I need?

For the example above, the dose is about 18.5 oz: one full 1 lb bag plus 2.5 oz from a second bag. Weigh the partial bag. Rounding up to two full bags would add much more chlorine than the selected target requires.

The same pool needs about 1.03 lb with a 73% product. Check “available chlorine” on your bag and use that percentage in the calculator.

Choose your treatment target

Use the treatment directions for your product and water condition to choose a target chlorine level. The 10 ppm starting example is editable. Algae treatment also depends on stabilizer (CYA), so check that reading before choosing the dose.

For a fecal contamination incident, use the CDC response procedure linked below. It includes a required chlorine level and contact time beyond an ordinary shock dose.

When can I swim after shocking?

Circulate for the time on your product label, then test the water. Swim once chlorine and pH meet the label’s re-entry limits. The amount added or the hours elapsed alone cannot tell you the remaining chlorine level.

If your test reads off-scale, use a test with a suitable range before deciding on another addition.

Add, circulate, then retest

Follow the product label for application and mixing time, then retest before adding more. Keep chemicals separate: never mix chlorine with acid or other chemicals.