Pool stabilizer calculator: how much cyanuric acid?
Stabilizer (cyanuric acid, CYA) keeps sunlight from burning off your chlorine. Enter your CYA test and target to get the dose — then the chlorine level that CYA calls for.
Enter your measurements
- CYA rise
- 40 ppm
- Free chlorine to keep at that CYA (7.5% convention)
- 3 ppm
- Per 10 ppm in this pool
- 13.4 oz
In short: stabilizer is added by weight — the rise you want times the water in your pool.
Rise: 40 − 0 = 40 ppm
40 mg per litre × 37,854 L = 1,514 g of cyanuric acid = 3.34 lb (53.4 oz)
Chlorine to keep at 40 ppm CYA: about 3 ppm (Trouble Free Pool’s 7.5% convention; CDC minimum with CYA: 2 ppm)
- Granular stabilizer dissolves slowly — often days. Follow the label (many say the skimmer, a sock, or a bucket), keep the pump running, and don’t backwash for a few days. Test CYA again after the dissolve time; the MAHC asks public pools to retest 24 hours after adding it.
- Stabilized chlorine adds CYA as you go: trichlor tablets about 0.6 ppm per ppm of chlorine, dichlor about 0.9. Using them? Aim lower and let them make up the rest.
Quick answers for common sizes
| Example | Answer |
|---|---|
| How much stabilizer for a 10,000 gallon pool | 2.5 lb (40.1 oz) |
| How much stabilizer for a 20,000 gallon pool | 6.68 lb (107 oz) |
Stabilizer for this pool, by target CYA (from the CYA above)
| Target CYA | Add this much stabilizer | Free chlorine to keep at that CYA (7.5% convention) |
|---|---|---|
| 20 ppm | 1.67 lb (26.7 oz) | 2 ppm |
| 30 ppm | 2.5 lb (40.1 oz) | 2 ppm |
| 40 ppm | 3.34 lb (53.4 oz) | 3 ppm |
| 50 ppm | 4.17 lb (66.8 oz) | 4 ppm |
| 60 ppm | 5.01 lb (80.1 oz) | 5 ppm |
| 70 ppm | 5.84 lb (93.5 oz) | 5 ppm |
| 80 ppm | 6.68 lb (107 oz) | 6 ppm |
Cyanuric acid binds loosely to chlorine and shields it from ultraviolet light. Without it, sunlight can destroy most of an outdoor pool’s chlorine in a few hours. With too much, chlorine works so slowly that algae gets a foothold unless you run chlorine high. The goal is enough, not more.
How much stabilizer: the formula
Granular stabilizer is essentially pure cyanuric acid, so the dose is plain arithmetic: 1 ppm is 1 mg per litre. In 10,000 gallons (37,854 L), 10 ppm is 379 g — 13.4 oz — and 30 ppm is 2.5 lb, exactly what one label says (2-1/2 lb per 10,000 gallons for 30 ppm). Liquid stabilizers vary by brand; one label gives 4 fl oz per 1 ppm per 10,000 gallons, which is what the liquid option here uses.
granular (g) = ppm rise × litres ÷ 1,000 granular (lb) ≈ 0.0834 × ppm rise × gallons ÷ 1,000 liquid (one label) = 4 fl oz × ppm rise × gallons ÷ 10,000
| Pool | +10 ppm | +30 ppm | +40 ppm | +50 ppm |
|---|---|---|---|---|
| 5,000 gal | 417.27 lb (6,676 oz) | 1,251.81 lb (20,029 oz) | 1,669.08 lb (26,705 oz) | 2,086.35 lb (33,382 oz) |
| 10,000 gal | 834.54 lb (13,353 oz) | 2,503.62 lb (40,058 oz) | 3,338.16 lb (53,411 oz) | 4,172.7 lb (66,763 oz) |
| 15,000 gal | 1,251.81 lb (20,029 oz) | 3,755.43 lb (60,087 oz) | 5,007.24 lb (80,116 oz) | 6,259.05 lb (100,145 oz) |
| 20,000 gal | 1,669.08 lb (26,705 oz) | 5,007.24 lb (80,116 oz) | 6,676.32 lb (106,821 oz) | 8,345.4 lb (133,526 oz) |
| 25,000 gal | 2,086.35 lb (33,382 oz) | 6,259.05 lb (100,145 oz) | 8,345.4 lb (133,526 oz) | 10,431.76 lb (166,908 oz) |
| 30,000 gal | 2,503.62 lb (40,058 oz) | 7,510.86 lb (120,174 oz) | 10,014.49 lb (160,232 oz) | 12,518.11 lb (200,290 oz) |
Worked pages: how much stabilizer for a 10,000 gallon pool and how much stabilizer for a 20,000 gallon pool.
What CYA level to aim for
- CDC: with CYA in the water, keep free chlorine at least 2 ppm (1 ppm without). The CDC recommends no CYA at all in hot tubs.
- Model Aquatic Health Code: CYA no higher than 90 ppm in public pools; a CYA-to-chlorine ratio above 45:1 is treated as an imminent hazard.
- Common practice: outdoor chlorine pools often run 30–50 ppm; salt pools 60–80 ppm. Indoor pools need little or none. The chlorine each level needs is in the chlorine and stabilizer calculator.
Adding stabilizer
- Read the label first; directions differ between granular and liquid products.
- Granular cyanuric acid dissolves slowly. Many owners put it in a sock or mesh bag in the skimmer basket or in front of a return and squeeze it daily; others pre-dissolve in a bucket of warm pool water. Don’t broadcast it on a vinyl floor where it can sit.
- Keep the pump running and don’t backwash or clean the filter for a few days, or undissolved granules go to waste.
- Retest after a week. CYA tests have coarse steps, so don’t chase a few ppm.
What you’ll need
- Stabilizer / conditioner (cyanuric acid)Budget price
Shields chlorine from sunlight. Dissolves slowly — follow the label (many say a skimmer or a sock), and don’t backwash for a few days.
See options on Amazon (opens in a new tab) - FAS-DPD drop test kit (chlorine, pH, TA, CH, CYA)Mid-range price
A drop-count kit reads free chlorine to 0.5 ppm (or 0.2 ppm), plus pH, alkalinity, calcium and stabilizer. Every dose on this site starts from a test, so this is the one thing worth buying first.
See options on Amazon (opens in a new tab) - Liquid pool chlorine (sodium hypochlorite)Budget price
Adds chlorine without stabilizer or calcium. Strength is printed on the label — commonly 10% or 12.5% — and it weakens with age and heat, so buy it fresh.
See options on Amazon (opens in a new tab)
As an Amazon Associate we earn from qualifying purchases. Links to products are affiliate links — they cost you nothing extra and help keep these calculators free.
Frequently asked questions
How much stabilizer raises CYA by 10 ppm?
About 13.4 oz of granular cyanuric acid per 10,000 gallons. By one liquid stabilizer’s label, about 40 fl oz per 10,000 gallons.
How much stabilizer do I add when opening a pool?
Test first — CYA only leaves with water, so a pool that wasn’t drained may still have most of last season’s. From zero to 40 ppm in 10,000 gallons is about 3.3 lb of granular. See how much stabilizer for a 10,000 gallon pool.
Can I swim after adding stabilizer?
Stabilizer itself isn’t a swimming hazard at normal levels, but follow your product’s label — and keep chlorine at the right level for the new CYA, which may be higher than before.
Why does my stabilizer reading not go up?
Granular stabilizer can take days to dissolve, and some of it may still be in the skimmer sock or the filter. Wait a week before retesting, and don’t backwash in the meantime.
Related guides
Sources
- Leslie’s — Pool Stabilizer (cyanuric acid) label (opens in a new tab) — 100% cyanuric acid; 2-1/2 lb per 10,000 gallons raises CYA by 30 ppm.
- Leslie’s — Instant Pool Water Conditioner Plus (liquid) label (opens in a new tab) — 4 oz in 10,000 gallons raises CYA 1 ppm; 1 gallon raises it 32 ppm per 10,000 gallons.
- CDC — Model Aquatic Health Code, 5th edition (2024), code (opens in a new tab) — Free chlorine minimum 1.0 ppm (2.0 with CYA, 3.0 in spas); pH 7.0–7.8; CYA at or below 90 ppm; CYA:FC above 45:1 is an imminent hazard; TA 60–180 ppm; turnover tables.
- CDC — Model Aquatic Health Code, 5th edition (2024), annex (opens in a new tab) — CYA reduces chlorine’s effectiveness; correcting total alkalinity for CYA by subtracting CYA ÷ 3.
- CDC Healthy Swimming — Home pool and hot tub water treatment and testing (opens in a new tab) — pH 7.0–7.8; free chlorine at least 1 ppm in pools (2 ppm with cyanuric acid) and 3 ppm in hot tubs; no CYA in hot tubs; test twice a day.
- Trouble Free Pool (hobbyist forum wiki) — CYA/chlorine relationship (opens in a new tab) — A widely used hobbyist convention, not an official standard: minimum FC 7.5% of CYA, SLAM (shock) level 40% of CYA, salt-water pools 5%.
- ICC Building Safety Journal (PHTA Recreational Water Quality Committee) — Trichlor: the dependable pool performer (opens in a new tab) — Trichlor is 90% available chlorine and adds 0.6 ppm cyanuric acid for each ppm of chlorine.
- CDC — Pool chemical injuries press release (2014) (opens in a new tab) — Never mix pool chemicals, especially chlorine products with acid; add chemical to water, never water to chemical.