Pool Stabilizer Calculator
Work out exactly how much cyanuric acid (stabilizer, conditioner) to add to your pool. If your CYA is already too high, the calculator tells you how much water to replace instead, because that is the only way down.
Stabilizer (CYA) Calculator
Chlorine pools: aim for 30 to 50 ppm. Saltwater pools: 60 to 80 ppm. Indoor pools need little to none.
What stabilizer actually does
Cyanuric acid acts like sunscreen for your chlorine. Unprotected chlorine in direct sunlight can lose half its strength in under an hour. At 30 to 50 ppm of CYA, chlorine lasts many times longer, which means you spend less and dose less often.
But more is not better. CYA also binds chlorine and slows it down. Past about 80 ppm, your chlorine reads fine on a test strip but sanitizes poorly. Algae outbreaks in pools with good chlorine readings are very often a high-CYA problem in disguise.
Why CYA creeps up over time
Trichlor tablets, the standard floater and feeder tabs, are roughly half stabilizer by weight. Every tab adds CYA that never leaves. A season or two of tabs can push a pool from 40 ppm to over 100.
Meanwhile, nothing removes it. Not shock, not sunlight, not filtration. Only draining part of your water and refilling with fresh dilutes CYA back down.
If your CYA keeps climbing, switch your daily chlorine source to liquid chlorine, which adds none, and save tabs for vacations. Our guide on high cyanuric acid covers the full recovery plan.
Where to buy
These are Amazon affiliate links that help support Pool Clarity at no cost to you.
Track your CYA automatically
The Pool Clarity app watches your stabilizer trend and warns you before it becomes a drain-and-refill problem. Free.
Related: Cyanuric acid explained · Muriatic acid calculator · All guides