Pool Stabiliser Calculator - How Much Cyanuric Acid To Add To Pool?

Planning on increasing the cyanuric acid concentration in your pool but not sure how much stabiliser to add? Use this stabiliser calculator to work out exactly how much to dose to your pool!

If you have too much cyanuric acid in your pool, this calculator can also work out how much water to drain and refill to lower your stabiliser concentration!

Pool Stabiliser Calculator

IMPORTANT: Cyanuric acid should be between 30 - 50 ppm. Do not exceed 50 ppm, otherwise you risk making your chlorine ineffective and creating unsafe conditions in your pool.

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How do I use this pool stabiliser calculator?

To calculate how much stabiliser to add to your pool, or how much water to drain and refill to your pool to lower the cyanuric acid concentration, you need to enter the following information:

  • Pool volume
  • Current CYA concentration
  • Desired CYA concentration
  • CYA product you will use (if increasing CYA concentration)

Once you enter this information, the calculator will tell you whether you need to increase or decrease your cyanuric acid concentration to hit your target level.

If you need to increase it, it will tell you how much of your stabiliser product you need to add.

If you need to decrease it, it will tell you how much water you need to drain and refill into your pool.

How much stabiliser do I put in my pool?

How much stabiliser you need to add to your pool depends on a few factors. As an example, let's look at a 50,000 L pool with a current CYA concentration of 15 ppm, and a target CYA concentration of 30 ppm.

The owner wants to use Zodiac UV Blockout as a stabiliser. It consists of 996 g/kg of cyanuric acid.

Cyanuric Acid Required = Volume x (Desired CYA - Current CYA) / 1000 / Product Concentration g/kg
Cyanuric Acid Required = 50,000 L x (30 mg/L - 15 mg/L) / 1,000 mg/g / 996 g/kg
Cyanuric Acid Required = 0.753 kg
Cyanuric Acid Required = ~ 750 g

In this example, a pool with low cyanuric acid, you need to add 750g of stabiliser to your pool.

How much water do I drain from my pool to lower CYA?

While cyanuric acid is essential for outdoor pools, having too much of it can make your chlorine ineffective.

The amount of water that you need to drain from your pool to lower CYA depends on a few different factors.

As an example, let's look at a 80,000L pool with a CYA concentration of 60 ppm that the owner wants to reduce to 50 ppm.

Water To Drain = Volume x (1 - (Final CYA / Current CYA))
Water To Drain = 80,000 L x (1 - (50 ppm / 60 ppm))
Water To Drain = 80,000 L x (1/6)
Water To Drain = ~ 13,300 L

In this case, you would need to drain about 13,000 L of water from your pool and refill it with fresh water to reduce the CYA concentration from 60 ppm down to 50 ppm.

Keep in mind that a dilution like this would reduce your chlorine concentration and salt concentration (in a salt water pool) substantially.

As you can see, it's much easier to add stabiliser than it is to take it away, so add it sparingly and carefully!


Noticed any errors in the calculator or just have general feedback? Let me know over at the contact page!

Louis from Pool Advisor


A chemical engineer by trade, Louis is committed to debunking myths in the pool industry by explaining the underlying chemistry and making it accessible to all.