Pool Cyanuric Acid PPM Calculator
Cyanuric acid (stabilizer) shields your chlorine from sunlight — outdoor pools want 30–50 PPM. Too much, though, and chlorine stops working ("chlorine lock"). This calculates the exact dose.
Calculator
Pool Cyanuric Acid PPM Calculator
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Cyanuric acid (stabilizer) shields your chlorine from sunlight — outdoor pools want 30–50 PPM. Too much, though, and chlorine stops working ("chlorine lock"). This calculates the exact dose.
How to use this calculator
- Enter pool volume.
- Enter target CYA (30–50 for outdoor).
- Get grams to add.
The formula
Grams = target PPM × liters ÷ 1,000.
What the inputs mean
The target is the concentration you want, in PPM. The volume is how much liquid you are treating. The current level is what is already in the water — the calculator only adds the difference, so you never double-dose. The result tells you exactly how much cyanuric acid to add.
Worked example
50,000 L pool targeting 40 PPM: 40 × 50,000 ÷ 1,000 = 2,000 g CYA.
Quick reference
| Pool size | CYA for 40 PPM |
|---|---|
| 25,000 L | 1,000 g |
| 50,000 L | 2,000 g |
From zero; test current level first.
Where you will actually use this
CYA only leaves the pool via splash-out and backwashing, so overdosing is a season-long problem.
- Outdoor pool startup
- Stabilizer top-ups
- After partial drain/refill
Mistakes that give wrong answers
- Overdosing (only fix is draining water)
- Adding it all at once without testing
Key takeaways
- Formula: CYA needed (g) = Target PPM × Pool volume (L) ÷ 1,000
- Remember: From zero; test current level first.
- Watch out for: Overdosing (only fix is draining water)
- Next step: run your own numbers in the calculator above, then verify with a measurement — calculated values are only as good as the inputs.
Frequently asked questions
What CYA level for outdoor pools?
30–50 PPM.
What happens with too much CYA?
Chlorine becomes ineffective — partial drain is the only fix.