How do you calculate how much chlorine to put in your pool?

1 gallon of 12% strength liquid chlorine will raise 120,000 gallons of water approximately 1ppm. For 10,000 gallons it takes about 9oz. to achieve 1ppm. PPM means parts per million not parts per moron. A 1-1.5ppm chlorine residual is usually sufficient to maintain a swimming pool as long as it is in a free and not combined form (chloromine). Public pools are closed down if the chlorine level exceeds 9ppm. 1 gallon of chlorine in a 10,000 gallon pool will exceed 14ppm. Use an oxidizer such as potassium monopersulfate to keep the chlorine in its free state and you won't turn your hair green (copper precipitates) or dissolve your children. If you're using calcium hypochlorite a quarter pound will raise 20,000 gallons to 1ppm. The practice of overdosing a pool with chlorine once a week is for lazy people that don't know chemistry or math. Chlorine is an oxidizer and can be harmful in large doses as it is easily absorbed through the skin. Take your choice.