Pool & Hot Tub Chemical Calculator

Per 10,000 gallons, roughly 10.7 fl oz of 12.5% liquid chlorine, about 2 oz by weight of 73% cal-hypo, or about 2.4 oz of 56% dichlor. The dose scales with volume and the ppm increase.

For a roughly rectangular pool, gallons = length × width × average depth (in feet) × 7.48. The calculator can do this for you if you switch to the dimensions mode.

Always test your water first, follow the product label, and add chemicals to water - never water to chemicals. Pre-dissolve cal-hypo and dichlor and add slowly. These are estimates; re-test after dosing.

Cyanuric acid level, pH, sunlight, and bather load all affect how fast chlorine is consumed, so real-world demand can exceed the simple dosing math. Re-test and adjust after each addition.

1 to 3 ppm is the ideal range for residential pools per the CDC; hot tubs run 3 to 5 ppm because hot water speeds up demand. Below 1 ppm the water stops sanitizing; above 5 ppm it irritates eyes and skin.

A standard 3-inch trichlor tablet (about 8 oz) releases roughly 5 ppm of free chlorine in 10,000 gallons as it dissolves. For an immediate boost, liquid chlorine works within hours while tablets take days.

UV light destroys unstabilized free chlorine in 1 to 2 hours. Keep cyanuric acid (CYA) between 30 and 50 ppm in outdoor pools to protect it. Without CYA you can lose more than 90% of your chlorine in a day in full sun.

Never mix liquid chlorine with cal-hypo or dichlor in the same container or in the return line: the reactions release toxic gas. You can alternate them on different days, but watch your CYA if you use dichlor or trichlor often.

Chlorine and pH, two to three times a week during active swim season. Alkalinity and CYA, every 2 to 4 weeks. Calcium, once a season. Take your water to a local pool store every month or two for a full test to confirm your home kit.