About this tool
The Cyanuric Acid (Stabilizer) Calculator is a free, in-browser pool tool that tells you exactly how much cyanuric acid (CYA, also sold as stabilizer or conditioner) to add to bring your pool to a target CYA reading. Cyanuric acid shields chlorine from being burned off by sunlight, so keeping it in range is what makes daytime chlorination actually work. Because CYA is added at roughly 99% purity and reads about 1:1 by weight, the dose is lb = gallons × Δppm ÷ 120,000 (equivalently gallons × 8.34 × Δppm ÷ 1,000,000), and in metric grams = litres × Δppm ÷ 1,000.
Everything is computed locally in your browser — nothing you enter is uploaded or stored. Enter your pool volume, current CYA, and target CYA and the tool returns the amount to add in pounds and ounces (US) or grams and kilograms (metric). As a sanity check, about 13 oz of stabilizer per 10,000 gallons raises CYA by roughly 10 ppm.
Cyanuric acid cannot be removed chemically — the only way to bring a high level down is to drain and dilute with fresh water. If your target is below the current reading the calculator switches to dilution mode and shows the fraction of the pool to drain and refill, drain % = (1 − target ÷ current) × 100. Typical targets are 30–50 ppm for a traditional chlorine pool and 60–80 ppm for a saltwater pool; over-stabilizing ("CYA lock") weakens chlorine, while too little lets the sun destroy it. CYA dissolves slowly, so add it via a sock in the skimmer and allow 24–48 hours before retesting.