How the doses are figured
Everything scales from one constant: raising any reading by 1 ppm in 10,000 gallons takes 0.0834 pounds of the pure substance. Divide by each product's active fraction (65% cal-hypo, 12.5% liquid chlorine, and so on) and multiply by your gallons and your gap — that's the whole trick, and it's the same arithmetic behind the dose charts printed on product labels. This calculator just does it for your exact numbers and answers in cups, quarts, and pounds instead of "per 10,000 gallons."
dose = 0.0834 lb × (target − current) × (gallons ÷ 10,000) ÷ active fraction
pH is the exception — it isn't a concentration, so acid and soda-ash doses depend on how much alkalinity is buffering the water. The pH section scales its dose by your TA reading and deliberately tells you to add in stages: overshooting pH downward is much more annoying than taking two passes.
A weekly routine that works
Test twice a week in season (chlorine and pH), with a full panel — alkalinity, CYA, calcium — every couple of weeks. Chlorine drifts down, pH usually drifts up, and everything else moves slowly. Enter the reading, add the dose, let the pump run, and you're done. Once balance is boring, check the saturation index occasionally — it's the early-warning system for scale and corrosion that individual readings can hide.
Frequently asked questions
What order should I adjust chemicals in?
Total alkalinity first — it's the buffer everything else leans on. Then pH, then chlorine, then stabilizer (CYA), then calcium. Fixing pH before alkalinity usually means fixing pH twice. Wait a few hours (with the pump running) and retest between adjustments.
Why is my dose different from what the bottle says?
Bottle instructions assume a round-number pool and a single-step change. This calculator scales the same published dose factors to your exact gallons and your exact gap between current and target reading. When the label and the calculator disagree meaningfully, trust the label — it knows the product's actual concentration.
Liquid chlorine, cal-hypo, dichlor, trichlor — which should I use?
Liquid chlorine adds nothing but chlorine (and a little salt) — the cleanest habit for regular dosing. Cal-hypo also raises calcium hardness; fine unless your CH is already high. Dichlor and trichlor carry stabilizer with every dose: convenient at first, but CYA only accumulates, and an over-stabilized pool needs draining to fix. If you shock with dichlor or run trichlor tabs all season, watch the CYA number.
How much shock do I need for a green pool?
A visibly green pool is beyond routine dosing — you're chasing roughly 10+ ppm of free chlorine, brushed and re-dosed until the water holds chlorine overnight. Use the chlorine section with a high target for the arithmetic, but expect several rounds, and keep swimmers out until chlorine returns to normal range and the water clears.
Is it safe to mix chemicals to save a trip to the pool?
Never. Chlorine products mixed with each other or with acid can ignite or release toxic gas — even "just" the residue in a shared measuring cup. One chemical at a time, rinse everything, add each chemical to water (never water to chemical), and let the pump circulate between additions.