CYA (Stabilizer) Calculator

Enter your pool volume, current CYA, and target — get the stabilizer dose in pounds, plus the level your chlorine target should track.

Don't know it? Use the pool volume calculator.

30–50 ppm typical; 60–80 for salt water pools.

Stabilizer to add
—
In ounces (by weight)—
ppm increase—
Suggested everyday FC at target—

CYA dissolves slowly — use the sock method and retest in 3–7 days before adding more. There's no practical way to lower it except draining water.

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The stabilizer dosing formula

lbs of CYA = (target ppm − current ppm) × gallons × 8.34 ÷ 1,000,000

Like salt, CYA dosing is pure ppm math — milligrams per liter converted through water's weight. The difference is the stakes: overshoot salt and the generator complains; overshoot CYA and you're draining water, because nothing removes it chemically.

A worked example

A 15,000-gallon pool at 10 ppm targeting 40 ppm needs 30 ppm more: 30 × 15,000 × 8.34 ÷ 1,000,000 ≈ 3.8 lbs of cyanuric acid. Dose 80% of it, wait most of a week, retest, and top up — patience here is what keeps you off the drain-and-refill path.

Why CYA and chlorine are a pair

CYA shields chlorine from UV, but it also binds some of it, so the right FC target scales with CYA — a common rule keeps everyday FC around 7.5% of the CYA level (40 ppm CYA → FC ≈ 3 ppm). Testing one without knowing the other is how pools end up "sanitized on paper" but green in practice.

Frequently asked questions

How much stabilizer do I add to my pool?

About 0.83 lbs of cyanuric acid raises CYA by 10 ppm in 10,000 gallons. Going from 0 to 40 ppm in a 15,000-gallon pool takes roughly 5 lbs.

What should my pool's CYA level be?

30–50 ppm for most chlorine pools; salt water pools often run 60–80 ppm because the cell works the chlorine harder. Indoor pools need none — CYA's only job is protecting chlorine from sunlight.

What happens if CYA is too high?

Chlorine becomes sluggish — the same FC sanitizes less, so algae gets a foothold even with 'good' readings. Above roughly 100 ppm, the practical fix is a partial drain and refill; no chemical lowers CYA reliably.

How do I add cyanuric acid?

The sock method: put the granules in an old sock, hang it in front of a return jet or in the skimmer basket (if your manual allows), and squeeze occasionally. It dissolves slowly — give it up to a week before trusting the test and adding more.

Related calculators

Pool Volume CalculatorHow many gallons your pool holds — the number everything else needs.Pool Chlorine CalculatorExact liquid chlorine dose to hit your target FC level.Pool Salt CalculatorPounds of salt to reach your SWG's target ppm.Pool Shock CalculatorThe right shock dose from your combined chlorine reading.