CYA Calculator
Estimate cyanuric acid adjustment using pool volume, current CYA and target level, with guidance for stabilizer additions and partial water replacement.
CYA Calculator
Enter measured values rather than estimates whenever possible. Results are planning guidance and must be checked against equipment manuals, chemical labels and local requirements.
How this estimate works
For raising CYA, the calculator converts the ppm increase to stabilizer mass. For lowering CYA, it estimates the fraction of water that must be replaced under ideal complete-mixing assumptions.
Improve calculator accuracy
Verify pool volume
Use construction records, internal measurements or a metered fill when available.
Use current readings
Test water or measure system conditions immediately before a significant adjustment.
Check product strength
Read the active ingredient, available strength and dosage table on the exact label.
Adjust in stages
For large changes, apply a partial amount, circulate, retest and refine.
Before applying the result
Do not combine incompatible chemicals, bypass equipment limits or rely on a calculator when measurements are uncertain. Wear the protective equipment required by the label and keep chemicals separated, dry and secured.
Frequently asked questions
What does cyanuric acid do in a pool?
Cyanuric acid stabilizes chlorine against ultraviolet degradation. Excessive CYA can also reduce chlorine disinfection effectiveness, so it should be measured and managed.
Can cyanuric acid be lowered chemically?
The dependable correction is usually partial water replacement, subject to local discharge rules. Products marketed for CYA reduction should be evaluated cautiously and used only according to their labels.
Do trichlor and dichlor raise CYA?
Yes. Stabilized chlorine products add cyanuric acid as they are used. Track CYA when these products are part of the sanitation program.
Should CYA be used in a hot tub?
CDC recommends not using cyanuric acid or chlorine products containing cyanuric acid in hot tubs.
Why should I add less stabilizer than the full estimate?
CYA is difficult to lower without water replacement. Adding in stages, circulating and retesting reduces the chance of overshooting.
How long should I wait before retesting CYA?
Follow the stabilizer label and test-method instructions. Complete dissolution and uniform circulation can take time.
Does evaporation lower CYA?
No. Evaporation removes water but leaves dissolved CYA behind. CYA falls when water containing it is removed and replaced.
How accurate are CYA tests?
Accuracy depends on the method, lighting, sample handling and reading range. Use a suitable test and repeat questionable results before a large water exchange.
Related Pool Equipment Guide resources
Use the result carefully
Use the calculated result to narrow the next step, then confirm it against the exact equipment manual or chemical label before making a purchase or adjustment.