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Free pool chemistry calculator

Start with your gallons, free chlorine and pH. Add more readings for a more complete plan, worked out by the same engine as the app.

No test yet? See a sample plan →

Your pool

Your readings

Only have free chlorine and pH? With your gallons, that’s enough to start.

A plan from those is less complete. What a blank changes:

  • Stabilizer (CYA): we use the lowest chlorine target, so your real target is probably higher.
  • Alkalinity (TA): we can say which way to move pH, but not how much to add.
  • Water temperature, hardness or alkalinity: we can’t run the scale-and-corrosion check. A ZIP can stand in for temperature.

Got a pool-store printout? Bring its numbers: FC, pH, TA, CYA and CH.

Test strips are dependable for chlorine and pH, and weakest on stabilizer and hardness — the two that set your chlorine target and your scale-and-corrosion check. Confirm those two with a drop kit, or a free store sample, a couple of times a season.

Your plan

Example — 20,000 gal plaster pool

Free chlorine
0.5 ppm
Stabilizer (CYA)
60 ppm
pH
7.5

Add 166.5 fl oz of Liquid Chlorine 10%

Free chlorine 0.5 ppm → 7 ppm, because 60 ppm of stabilizer raises the target.

20,000 gal × 6.5 ppm ÷ 1,000,000 ÷ 10% × 128 fl oz/gal → 166.4 fl oz, rounded to 166.5 fl oz

That is the whole calculation — your pool’s volume, how far the reading has to move, and the strength of the product. Where our numbers come from →

Put your own readings in on the left and tap “Get my plan” to replace this with yours.

That dose is real — the same deterministic engine the app runs, same answer every time.

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Questions about this calculator →