Pool Chlorine Calculator

Reviewed 2026-04

CYA (cyanuric acid, the chlorine stabilizer) -aware dosing for liquid chlorine, bleach, dichlor, or cal-hypo. Enter your pool size, current FC (free chlorine), and CYA level. Get exact ounces.

Built on CDC and ANSI pool-water standards

Pool volume (gallons)

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Know your exact size? Use the Volume Calculator →

Current FC (ppm)

Target FC (ppm)

CYA level (ppm)

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Don't have a CYA test? Type 30 ppm as a safe default for outdoor pools (typical range 30–50 ppm). Basic strip tests don't measure CYA. For exact dosing you need a 4-in-1 test kit (Amazon →) or want to dose stabilizer? Use our CYA dosing calculator →

Chlorine source

10% sodium hypochlorite (pool store liquid)12.5% sodium hypochlorite (pool store liquid, stronger)8.25% bleach (Clorox Regular)6% bleach (generic)Dichlor granular (56% Cl)Cal-hypo (65% Cl)

With your CYA at 30 ppm, your minimum effective chlorine is 2 ppm, not the standard 1–3 ppm.

Your current FC of 1.0 ppm means your pool is effectively unsanitized despite showing chlorine on a test strip.

This calculator will dose chlorine to reach 3 ppm. That is the safe minimum for your stabilizer level.

Source: O'Brien et al. (1974); TFP CYA/Chlorine chart.

Popular liquid chlorine

Enter your pool data above for personalized quantities

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Top Pick

Champion

Liquid Chlorine (1-Pack) · 1 gallon jug (12.5%)

★★★★4.3 (8)

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Clorox

Disinfecting Bleach (8.25%) · 121 oz jug (8.25%)

★★★★½4.8 (1,945)

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ProSide

Chlorinating Liquid (10%) · 2-gallon case (10%)

★★★★4.3 (8)

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HOCl effectiveness by pH

The active sanitizing form of chlorine is HOCl (hypochlorous acid). Its effectiveness varies significantly with pH.

pH	Active HOCl %	Note
7.0	73%	High effectiveness
7.2	66%	Good
7.4	55%	Optimal: target range
7.6	44%	Acceptable
7.8	33%	Getting low
8.0	25%	~25%, NOT <3% (common error)
9.0	3%	<3%, this is where the "3%" figure applies

Source: ANSI/PHTA/ICC-11 §5.3 chlorine-species pH equilibrium tables (canonical source IDs CS-013 and CS-014). At pH 8.0: only ~25% HOCl (not <3%; that only applies at pH 9.0+).

Frequently asked questions

How much chlorine do I need to add to my pool?

The amount depends on your pool volume, current free chlorine (FC) level, and CYA level. Use the calculator above for an exact dose. As a general reference, raising FC by 1 ppm in a 10,000-gallon pool requires about 12.8 oz of liquid chlorine (10% sodium hypochlorite). Always retest after 4–6 hours.

What free chlorine level should I target based on my CYA?

Free chlorine targets scale with CYA. With 0 ppm CYA, target FC of 2–4 ppm. With 30 ppm CYA, target 2–5 ppm. With 50 ppm CYA, target 3–7 ppm. With 80 ppm CYA, target 5–10 ppm. The minimum safe FC is approximately 7.5% of your CYA level (the "FC/CYA ratio" or SLAM floor).

What is the difference between trichlor and dichlor?

Trichlor (trichloroisocyanuric acid) is a slow-dissolving tablet or stick with ~90% available chlorine and contains CYA stabilizer; each tablet raises CYA over time. Dichlor (sodium dichloroisocyanurate) is a fast-dissolving granular chlorine with ~56–62% available chlorine, also containing CYA. If your CYA is already high, switch to an unstabilized chlorine source like liquid chlorine or cal-hypo.

When is the best time to add chlorine to a pool?

Add chlorine in the evening or after sunset. UV sunlight degrades unstabilized chlorine rapidly. Up to 90% can be lost in 2 hours without CYA. Evening dosing lets the chlorine circulate overnight when demand is highest. If using stabilized chlorine (trichlor, dichlor), UV degradation is less of a concern.

Is liquid chlorine better than chlorine tablets?

Liquid chlorine (sodium hypochlorite) raises no CYA, letting you control stabilizer levels independently. It is the preferred choice when CYA is already near or above 50 ppm. Tablets are convenient for slow, steady maintenance chlorination but steadily raise CYA. Most pools using only tablets end up with uncontrolled CYA levels by mid-season.

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How we calculate this
Our formulas follow ANSI pool-water standards and are validated against CDC pool-water health code guidelines. We show you the math so you can verify every result. Questions or corrections? Please contact us.