How much bleach to add to your pool

With 8.25% bleach, it takes 1.45 fl oz. A 3 ppm top-up (FC 1 to 4) is about 6.2 fl oz of 6% bleach per 1,000 gallons.

Calculator: bleach %, gallons, target FC

Enter your pool volume, your current FC, the level you want, and your stabilizer (cyanuric acid, CYA) reading. Pick the percent printed on your bottle, or type it if it's different. The calculator shows the dose, the amount per 1 ppm for your pool, and the FC range that fits your CYA, so you don't aim too low or too high.

Unscented household bleach has the same active chemical as pool liquid chlorine: sodium hypochlorite. It is weaker and labeled differently. Dosed correctly, it chlorinates a pool as well as any pool-store product.

Which bleach (plain, unscented, no splashless)

• Use: plain, regular bleach whose label lists sodium hypochlorite as the only active ingredient, with the percent printed on it.
• Avoid scented bleach: fragrance and other additives have no place in pool water.
• Avoid "splashless" or thickened bleach: it's formulated for laundry, not for treating water.
• Avoid "color-safe" bleach: it's usually hydrogen peroxide, not chlorine, and won't raise FC.
• Check the date and store it cool: sodium hypochlorite loses strength over time, faster in heat. A bottle that sat in a hot garage all summer delivers less than its label says.

Bleach % vs pool chlorine %: weight vs trade percent

A gallon of "8.25%" bleach and a gallon of "10%" pool chlorine don't compare as 8.25 to 10 in strength, because the two percents are measured differently.

• Household bleach is labeled in percent sodium hypochlorite by weight (PHTA; EPA labels).
• Pool liquid chlorine is labeled in trade percent: grams of available chlorine per liter, divided by 10 (PHTA).

When we convert bleach to the same basis (using density from the OxyChem handbook and sodium hypochlorite's available-chlorine factor), one gallon in 10,000 gallons raises FC by:

Because bleach is a bit denser than water, the weight percent slightly understates its chlorine per gallon. That's why 8.25% bleach behaves like about 8.8% pool chlorine.

Cost per ppm vs liquid chlorine

Compare cost per ppm, not per bottle. The math is short:

Cost for +1 ppm in 10,000 gal = price per gallon ÷ ppm per gallon (table above).

So a gallon of 6% bleach has to cost less than about 62% of a gallon of 10% pool chlorine to be the better deal (6.2 ÷ 10). Bleach jugs are often smaller than a gallon, so convert first. Prices vary a lot by region and season, so put your own into the chemical cost calculator, which does this for every product. Bleach is usually worth it when you use a little (small pools, kiddie pools, top-ups) or when pool chlorine isn't available nearby.

Chart

The table gives the amount for +1 ppm at common pool sizes. Multiply by the ppm you need: for FC 1 → 4, multiply by 3. For all products side by side, see how much chlorine to add. For pool-store jugs, use the liquid chlorine calculator.

Amount for +1 ppm free chlorine, by pool size

Pool size	Household bleach 6%	Household bleach 8.25%
500 gal	1.0 fl oz30 mL	0.7 fl oz21 mL
1,000 gal	2.1 fl oz61 mL	1.4 fl oz43 mL
2,000 gal	4.1 fl oz122 mL	2.9 fl oz86 mL
3,000 gal	6.2 fl oz183 mL	4.3 fl oz129 mL
4,000 gal	8.2 fl oz244 mL	5.8 fl oz172 mL
5,000 gal	10 fl oz305 mL	7.2 fl oz214 mL
6,000 gal	12 fl oz366 mL	8.7 fl oz257 mL
7,000 gal	14 fl oz427 mL	10 fl oz300 mL
8,000 gal	16 fl oz488 mL	12 fl oz343 mL
10,000 gal	21 fl oz609 mL	14 fl oz429 mL
12,000 gal	25 fl oz731 mL	17 fl oz515 mL
15,000 gal	31 fl oz914 mL	22 fl oz643 mL
20,000 gal	41 fl oz1.22 L	29 fl oz858 mL
25,000 gal	52 fl oz1.52 L	36 fl oz1.07 L
30,000 gal	62 fl oz1.83 L	43 fl oz1.29 L
40,000 gal	82 fl oz2.44 L	58 fl oz1.72 L

Multiply by how many ppm you need. Example: FC 1 → 4 is +3 ppm. Each size links to its full dose chart.

Download this data (CSV)

Worked example for a 15,000-gallon pool: +1 ppm takes about 31 fl oz of 6% bleach or 22 fl oz of 8.25%. Going from 1 to 4 ppm takes 93 fl oz of 6% (about three-quarters of a gallon) or 65 fl oz of 8.25%. Every dose for that size on one page: 15,000-gallon pool. More pool sizes: dosing by pool size.

FAQ

How much bleach equals pool shock?

A 1 lb bag of 65% cal-hypo shock adds about 7.8 ppm to 10,000 gallons. The same rise takes about 1.25 gallons (161 fl oz) of 6% bleach or 113 fl oz of 8.25%. Use bleach as shock only if its label has pool directions; many household bleach labels don't. That label sets the amount, usually per 10,000 gallons, so scale it to your pool. The label also tells you when swimming can resume. If algae is still there after a few days of label doses, call a pool professional. Steps: how to shock a pool.

Is bleach the same as pool chlorine?

Chemically, yes: both are sodium hypochlorite, and plain unscented bleach works as pool chlorine. The differences are strength (6–8.25% by weight vs 10–12.5% trade percent), how the percent is measured, and additives in some bleaches. Dose by the percent on your bottle, not by "cups per pool".

Sources

• PHTA fact sheet, Sodium hypochlorite (trade percent vs weight percent, decomposition): phta.org
• OxyChem, Sodium Hypochlorite Handbook (density and conversion formulas): PDF
• EPA pesticide label 5813-1, Clorox Regular-Bleach (2011): epa.gov (PDF)
• Orenda, Understanding labeled chlorine percentages: blog.orendatech.com
• CDC, Model Aquatic Health Code 2024, Annex: cdc.gov (PDF)