Pool stabilizer calculator
To raise stabilizer (cyanuric acid, CYA) from 0 to 40 ppm in a 15,000-gallon pool, add about 5.0 lb of granular stabilizer.
Always follow your product’s label directions. Pool and spa chlorine, bromine, shock and algaecides are EPA-registered pesticides: use products labeled for pool or spa use, and don’t swim or soak until levels are within the limit on your product’s label. If this page and a label disagree, the label wins.
On this page (9 sections)
Only draining lowers CYA, so never go above your target.
Calculator: gallons, current and target CYA
Enter your pool volume, your CYA from a test, your target, and the strength of your product. Granular stabilizer is close to pure cyanuric acid, so leave purity at 100% unless your label says otherwise. If you type a target below your current level, the calculator switches to the only thing that works in that direction: how much water to replace.
Two testing notes before you dose. Most CYA tests are hard to read above about 100 ppm, so dilute the sample 1:1 with tap water and double the result (PHTA). And a hot sample reads low, so test at pool temperature, not with water that sat in the sun.
Target CYA: 30–50 chlorine, 60–80 salt
Stabilizer shields chlorine from sunlight, but it also holds part of the chlorine in reserve. The CDC's Model Aquatic Health Code (2024 Annex) explains that the active chlorine stays about the same when the ratio of CYA to free chlorine stays the same. So every 10 ppm of CYA you add raises the free chlorine (FC) level you need to keep. Our targets:
| Pool type | Target CYA | Free chlorine to keep at that CYA |
|---|---|---|
| Liquid chlorine, bleach, tablets | 30–50 ppm | 2.5–4.5 ppm at CYA 30; 4–6 ppm at CYA 50 |
| Salt water generator | 60–80 ppm (check your cell manual) | 3–5 ppm at CYA 60; 4–6 ppm at CYA 80 |
| Indoor pool or hot tub | none needed | hot tubs: 3–4 ppm FC, no CYA (CDC) |
Chlorine targets from our engine: minimum about 7.5% of CYA (5% for salt cells), at least 2 ppm with CYA. Full table on pool chlorine levels.
Salt cell makers do not all agree. Hayward's AquaRite manual allows stabilizer up to 80 ppm, while Pentair's IntelliChlor quick start guide says to set it between 30 and 50 ppm. Use your own cell's manual. The salt water pool care guide covers the rest of the routine. If you want to know what CYA actually does in the water, read what is cyanuric acid.
Chart: stabilizer by pool size
Pounds of granular stabilizer for +10 ppm and for a new fill (0 → 40 ppm). Each pound raises CYA by about 12 ppm in 10,000 gallons. Each size links to its full dose sheet.
| Pool size | +10 ppm | 0 → 40 ppm |
|---|---|---|
| 500 gal | 0.65 oz | 2.7 oz |
| 1,000 gal | 1.3 oz | 5.3 oz |
| 2,000 gal | 2.7 oz | 10.7 oz |
| 3,000 gal | 4.0 oz | 1.0 lb |
| 4,000 gal | 5.3 oz | 1.35 lb |
| 5,000 gal | 6.7 oz | 1.65 lb |
| 6,000 gal | 8.0 oz | 2.0 lb |
| 7,000 gal | 9.3 oz | 2.35 lb |
| 8,000 gal | 10.7 oz | 2.65 lb |
| 10,000 gal | 13.4 oz | 3.35 lb |
| 12,000 gal | 1.0 lb | 4.0 lb |
| 15,000 gal | 1.25 lb | 5.0 lb |
| 20,000 gal | 1.65 lb | 6.7 lb |
| 25,000 gal | 2.1 lb | 8.35 lb |
| 30,000 gal | 2.5 lb | 10.0 lb |
| 40,000 gal | 3.35 lb | 13.4 lb |
Each size links to its full dose chart.
Granular vs liquid stabilizer
Granular (dry) stabilizer is cyanuric acid powder or granules. It is cheap per ppm but dissolves slowly: often several days, longer in cold water. Put it in a clean sock or mesh bag in the skimmer basket, or in a bucket of warm pool water that you top up and stir, and keep the pump running. Don't sprinkle it over a vinyl liner, where undissolved granules can sit on the floor.
Liquid stabilizer is a suspension or solution that mixes in within a day and shows up on a test much sooner. It costs more per ppm because you are paying for water too. The label states how much it contains. Enter that in the purity field. For example, a product with 50% cyanuric acid by weight needs twice the weight of granules: 10.0 lb instead of 5.0 lb for 0 → 40 ppm in 15,000 gallons. Always follow the product label for its own dose.
Tablets add CYA too: how fast
Trichlor tablets and pucks are about half stabilizer by weight. PHTA puts it at 0.6 ppm of CYA added for every 1 ppm of chlorine they deliver. Dichlor granules add 0.9 ppm. So the faster your pool uses chlorine, the faster CYA climbs, whatever the pool size:
| Chlorine your pool uses per day | CYA added per week | CYA added in 30 days |
|---|---|---|
| 1 ppm | 4.2 ppm | 18 ppm |
| 2 ppm | 8.4 ppm | 36 ppm |
| 3 ppm | 12.6 ppm | 54 ppm |
| 4 ppm | 16.8 ppm | 72 ppm |
0.6 × daily chlorine use × days (PHTA ratio). Splash-out, backwashing, and rain overflow remove some CYA with the water, so real pools rise a little more slowly.
This is why a pool that starts the summer at 30 ppm on tablets can pass 60–80 ppm by August. If you use tablets, you may not need to add stabilizer at all: start lower and let the tablets bring it up. The chlorine tablet calculator projects your CYA week by week.
Retest after 3–7 days
Granular stabilizer can take days to dissolve and spread, and a test taken too early reads low. The common mistake is to see "still 20" on day two and add another dose, then find 70 a week later. Wait at least 5 days after granules (a day or two after liquid stabilizer), keep the pump running, brush any granules that settle, and then retest. The 3–7 day window is common pool-care practice rather than a published standard. While you wait, keep chlorine at the level for your target CYA, since that is where the water is heading.
Overshot? Only water removes CYA
No chemical you can buy removes stabilizer reliably. It leaves when water leaves: splash-out, backwashing, rain overflow, and draining. To get from your level to your target, replace this share of the water (fill water with no CYA):
- 50 → 40 ppm: replace 20% of the water.
- 60 → 40 ppm: replace about 33%.
- 80 → 40 ppm: replace 50%.
The guide to lowering CYA has a drain calculator that also accounts for CYA in your fill water, plus what to know before draining a vinyl-liner or in-ground pool.
FAQ
Does baking soda raise CYA in pool?
No. Baking soda is sodium bicarbonate: it raises total alkalinity and, slightly, pH. It contains no cyanuric acid. Only stabilizer, trichlor, and dichlor add CYA.
Will shocking a pool raise cyanuric acid?
Only if the shock is dichlor or trichlor. Dichlor adds about 0.9 ppm of CYA for every 1 ppm of chlorine it adds, so a dichlor shock that raises free chlorine by 10 ppm also adds about 9 ppm of CYA, whatever the pool size. Liquid chlorine, bleach, cal-hypo (calcium hypochlorite), and non-chlorine (MPS) shock add none.
How long does pool stabilizer take to dissolve?
Granular stabilizer often takes several days, longer in cold water. Liquid stabilizer mixes in within a day. Keep the pump running, brush any granules that settle, and retest after at least 5 days for granules (a day or two for liquid) before you add more.
Can I put stabilizer in the skimmer?
Put granules in a clean sock or mesh bag in the skimmer basket, or dissolve them in a bucket of warm pool water that you top up and stir, with the pump running. Don't sprinkle them over a vinyl liner, where undissolved granules can sit on the floor. Always follow the product label.
Sources
- CDC, Model Aquatic Health Code 2024, Annex (CYA and free chlorine): cdc.gov (PDF)
- PHTA fact sheet, Dichlor (CYA added per ppm of chlorine): phta.org
- Hayward, AquaRite manual: PDF
- Pentair, IntelliChlor SCG Quick Start Guide and Tips (P/N 520943 Rev. D): PDF
- CDC, Home pool and hot tub water treatment and testing: cdc.gov