Pool chemical calculator
Enter the volume and what your test kit says. Get the dose for each chemical — listed in the order a pro actually adds them, because alkalinity moves pH and doing it backwards means doing pH twice.
Pool volume
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Your test readings
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Products you carry
What to add, in order
- Never mix chemicals — add one at a time with the pump running and let it circulate before the next. Acid and chlorine together produce chlorine gas.
- Always add acid to water, never water to acid, and never pour it near the skimmer.
- pH response depends heavily on alkalinity — add about two thirds of a pH dose, circulate, then retest.
- The product label governs. These are standard doses per 10,000 gallons; your product's concentration may differ.
Why the order matters
Total alkalinity is a buffer: it resists pH movement, and changing it drags pH along with it. Adjust pH first and you will adjust it again after you fix alkalinity — so alkalinity goes first, every time. Then pH, then calcium hardness, then stabilizer, and sanitizer last, once the water will actually hold it.
This is the same sequence in our pool water chemistry guide; the calculator just does the arithmetic.
The chlorine / CYA relationship
The single most misunderstood number in pool chemistry. Cyanuric acid protects chlorine from UV — without it, an outdoor pool loses most of its free chlorine in a few hours of sun. But CYA also binds chlorine, and the more of it there is, the more free chlorine you need to sanitize at the same rate.
A pool at 80 ppm CYA sitting at 2 ppm free chlorine is not "in range" — it is under-sanitized and will grow algae while the test strip looks fine. The widely used rule is to hold free chlorine at roughly 7.5% of the CYA reading, so 40 ppm CYA wants about 3 ppm FC and 80 ppm wants about 6. This calculator targets that ratio rather than a flat 1–3 ppm.
The trap that follows: trichlor tabs and dichlor add CYA with every dose. A pool run on tabs all season climbs steadily until chlorine stops working — and since nothing removes CYA, the only fix is draining and refilling part of the water.
Standard doses per 10,000 gallons
| To move | Add | Amount |
|---|---|---|
| Free chlorine +1 ppm | Liquid chlorine 12.5% | 10.7 fl oz |
| Free chlorine +1 ppm | Cal hypo 73% | 1.8 oz wt |
| Alkalinity +10 ppm | Sodium bicarbonate | 1.4 lb |
| pH −0.2 | Muriatic acid 31.45% | 12 fl oz |
| pH +0.2 | Soda ash | 6 oz wt |
| Calcium hardness +10 ppm | Calcium chloride 77% | 1.25 lb |
| Cyanuric acid +10 ppm | Stabilizer (CYA) | 13 oz wt |
Frequently asked questions
What order should I add pool chemicals in?
Total alkalinity first, because it buffers pH and moving it moves pH with it. Then pH, then calcium hardness, then cyanuric acid, and sanitizer last. Add one at a time with the pump running.
How much chlorine do I need per 10,000 gallons?
About 10.7 fl oz of 12.5% liquid raises free chlorine 1 ppm in 10,000 gallons — roughly 1.8 oz by weight for 73% cal hypo. The calculator scales that to your volume and the gap to your target.
How do I lower cyanuric acid?
You can't. No chemical removes CYA — the only practical fix is dilution: drain a portion and refill. To halve it you replace about half the water.
Should free chlorine be based on cyanuric acid?
Yes, for a stabilized outdoor pool. A widely used rule is free chlorine at about 7.5% of CYA. A flat 1–3 ppm target on a high-CYA pool is how pools grow algae while testing "in range".
Is this a substitute for testing?
No — it converts a test result into a dose. Real pools vary, pH response especially, so dose partially and retest. The product label governs over any calculator.
Log the readings, not just the dose
SplashPilot Pro records every reading and chemical added against the stop as the tech closes it — so the service history is there when a customer asks why the pool went green.
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