Pool Cyanuric Acid Calculator
Reviewed by Hamza Gujjar, Algorithm Architect & Software Developer
Last updated: July 27, 2026Protecting chlorine from sunlight
Unstabilized chlorine breaks down within a couple of hours of direct sunlight exposure - cyanuric acid (also called stabilizer or conditioner) binds loosely with chlorine, slowing its destruction by UV rays without preventing it from sanitizing the water.
Worked example
For a 20,000-gallon pool currently at 20 ppm CYA, targeting 50 ppm:
Dose = (20000/10000) x ((50-20)/10) x 13 = 78.0 oz cyanuric acid
Cyanuric acid should typically stay between 30-50 ppm for outdoor pools - levels much above 100 ppm can suppress chlorine's sanitizing power in a phenomenon known as chlorine lock, even when free chlorine test readings still look adequate.