Pool shock calculator

Stabilizer (cyanuric acid) shields chlorine from the sun, but it also slows it down. So the chlorine level that counts as a "shock" rises with stabilizer: about 40% of your stabilizer reading, and never less than 10 ppm.

We take the gap between your chlorine now and that shock level, and work out how much of your product closes it for your pool.

The product label always wins — if it says something different, follow the label.

Because a pool with stabilizer 80 needs twice the chlorine of one with stabilizer 40 to do the same job. A fixed bag count under-shocks some pools and wastes chlorine in others.

When the water is green or cloudy, after heavy use or a storm, or when combined chlorine is high. Shock in the evening, with the pump running, and stay out until chlorine is back in its normal range.