How the calculator works
Chlorine dosing is straightforward arithmetic once you know three things: how much water you have, how far you need to raise free chlorine, and how strong your product is.
- ppm means milligrams per liter. Raising 10,000 gallons (37,854 liters) by 1 ppm takes 37.9 grams of available chlorine.
- Liquid chlorine strength is sold as grams of available chlorine per 100 mL. A 10% product has 10 grams per 100 mL.
- Dry products (cal-hypo, dichlor) list “available chlorine” as a percentage of their weight.
So the amount of product is simply the chlorine you need divided by the product’s strength. The calculator then rounds the result to sensible measuring units.
| Product (typical strength) | Amount to raise 10,000 gal by 1 ppm | Side effects |
|---|---|---|
| Liquid chlorine, 10% | 12.8 fl oz | Adds salt over time |
| Liquid chlorine, 12.5% | 10.2 fl oz | Adds salt over time |
| Household bleach, 6% | 21.3 fl oz | Adds salt over time |
| Cal-hypo, 65% | 2.1 oz (by weight) | Adds ~0.7 ppm calcium hardness per 1 ppm |
| Dichlor, 56% | 2.4 oz (by weight) | Adds ~0.9 ppm CYA per 1 ppm |
| Trichlor, 90% | 1.5 oz (by weight) | Adds ~0.6 ppm CYA per 1 ppm; very acidic |
The side effects come straight from the chemistry: dichlor and trichlor are built on cyanuric acid, so every dose leaves stabilizer behind, and cal-hypo leaves calcium.
Why your target depends on CYA
Cyanuric acid (stabilizer) protects chlorine from sunlight, but it also holds most of the free chlorine in a loosely bound reserve. Only the unbound part, hypochlorous acid, does the fast germ-killing. More CYA means you need more free chlorine for the same effect.
That’s why this calculator asks for CYA. It suggests:
- a minimum of about 7.5% of your CYA (never below CDC’s 1 ppm),
- a daily target range above that, so normal sun loss doesn’t drop you below the minimum by evening,
- a shock level of about 40% of CYA, for algae and problems. Use the shock calculator for that.
These ratios are widely used homeowner guidance, rooted in the chlorine–cyanuric acid chemistry. They aren’t a regulation. Public pools follow their state code, which is often based on CDC’s Model Aquatic Health Code.
Reading your result
The big number is the amount of product to add now to reach your target. If you’re already at or above target, you’ll see that instead. Treat it as an estimate:
- Liquid chlorine weakens as it sits, especially in heat, so an older jug delivers less than its label says.
- Test kits read in steps (often 0.5 ppm), so both your starting number and your retest carry some uncertainty.
- Add the dose, circulate, then retest before adding more.
Assumptions and limitations
- Treats ppm as milligrams per liter and uses the strength printed on your product label. Liquid chlorine and bleach lose strength with age and heat, so an old jug delivers less than calculated.
- Household bleach is labeled by weight, which makes it a few percent stronger than our liquid-chlorine math assumes; the difference is smaller than a home test kit can detect.
- Target ranges based on CYA are widely used homeowner guidance, not a regulation. CDC's floor is 1 ppm for pools.
- The dose raises chlorine once. Algae or heavy contamination keeps using chlorine; use the shock calculator for those.
Key terms
Common questions
How much liquid chlorine raises a 10,000-gallon pool by 1 ppm?
About 12.8 fluid ounces of 10% liquid chlorine, or about 10.2 fluid ounces of 12.5%. Double the pool size and you double the amount.
Can I use household bleach instead of pool chlorine?
Yes, if it's plain, unscented bleach with no added detergents or "splash-less" thickeners. It's the same chemical (sodium hypochlorite), just weaker (usually 6% to 8.25%), so you need more of it.
What free chlorine level should my pool have?
CDC recommends at least 1 ppm in pools. With stabilizer (CYA) in the water, you need more, because CYA holds most of the chlorine in reserve. A common rule is to keep free chlorine at no less than 7.5% of your CYA level: 3 ppm at 40 ppm CYA, for example.
How long after adding chlorine can I swim?
Once the chlorine has circulated (about 30 minutes for liquid chlorine) and a retest shows free chlorine within your normal range and pH between 7.2 and 7.8. Check the product label, which may give a longer wait.
Sources and methodology references
- Home pool and hot tub water treatment and testing, US Centers for Disease Control and PreventionFree chlorine at least 1 ppm in pools and 3 ppm in hot tubs; pH 7.2–7.8.
- Model Aquatic Health Code, US Centers for Disease Control and PreventionPublic-pool code; with cyanuric acid, minimum 2 ppm free chlorine and CYA no higher than 90 ppm (2018 edition).
- Pool School (chlorine/CYA chart and methods), Trouble Free PoolHomeowner guidance relating free chlorine targets to CYA: minimum about 7.5% of CYA, shock about 40%.
Published October 2, 2026. Results are estimates. See how our calculators work.
Spotted a wrong result or an outdated source? Report a problem with this calculator.
Related tools
- Pool shock calculatorWork out the shock level your pool actually needs and how much product gets you there. For algae it depends on your stabilizer; for a "chlorine smell" it depends on combined chlorine.
- CYA (stabilizer) calculatorGet the stabilizer amount to raise CYA, or the share of water to replace to lower it, plus the free chlorine level your new CYA calls for.
- Pool volume calculatorWork out how many gallons your pool holds from a few tape-measure readings. Every chemical dose depends on this number.
- pH calculatorFind how much acid lowers your pH, or how much soda ash raises it. The dose comes from a water-chemistry model that accounts for your alkalinity.
Related guides
- Cyanuric Acid (Pool Stabilizer): How Much You Need and Why It MattersStabilizer stops sunlight from destroying chlorine, but it also raises the chlorine level your pool needs. How CYA works, good levels, and how to raise or lower it.Read the guide (3 min)
- Pool Water Chemistry for Beginners: What Each Test Number MeansWhat free chlorine, pH, alkalinity, CYA, calcium hardness and combined chlorine actually tell you, which ones matter most, and what order to fix them in.Read the guide (4 min)
- How to Shock a Pool (and How Much Shock You Actually Need)How to shock a pool so it actually works. Find the right chlorine level for your stabilizer, choose a product, and hold the level until the job is done.Read the guide (4 min)
- How to Lower (or Raise) Pool pH SafelyWhy pool pH drifts up, how to bring it down with muriatic or dry acid, how to raise it, and why your alkalinity decides how much acid you actually need.Read the guide (3 min)