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Reference

Questions about the free calculator

The six things people ask before and after they get a dose from the free calculator, answered plainly.

Is the calculator really free?

Yes, permanently, and it does not need an account. It is the same chemistry engine paying subscribers use — not a preview of it and not a trial. Nothing you type here is stored.

Do I need to make an account to get a dose?

No. Enter your volume and whatever readings your kit gave you and you get a real dose back. An account is what lets the app remember your pool between tests, watch the weather, and check whether a dose actually worked — none of which a one-shot calculator can do.

What if I do not know how many gallons my pool holds?

Use “Not sure? Help me estimate it” under the volume field. It asks for the shape and rough dimensions and works the volume out. Volume is the one number the engine cannot proceed without, because every dose is proportional to it.

Why does it ask for stabilizer (CYA) to work out chlorine?

Because stabilizer decides how much chlorine your pool needs to hold. The same 2 ppm of free chlorine is plenty at 30 ppm of stabilizer and not nearly enough at 80. A calculator that ignores stabilizer is guessing at the number that matters most.

How do I know the amount is right?

Chlorine, alkalinity, stabilizer, calcium and salt doses each show their own arithmetic — your volume, how far the reading has to move, and the strength of the product — in the “Why this amount?” panel under the result. A pH dose does not: it comes from an acid-demand estimate rather than a formula, and printing one would be a plausible-looking lie. The engine is deterministic and versioned: the same readings always produce the same answer, and no AI writes a dose.

Why did it refuse to give me a dose?

It refuses on purpose in two cases: no pool volume, and readings that are outside what a test kit can physically produce. Both are places where an answer would be worse than no answer, so it tells you what is missing instead of guessing.

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