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Reviewed · Prices checked October 2026 · How we calculate

Pool Chlorine Calculator: How Much Liquid Chlorine or Bleach to Add

Enter your pool's gallons, your free chlorine reading and where you want it. You get the amount of liquid chlorine, bleach, cal-hypo or dichlor to add, and the jugs or bags to buy.

Pool and chlorine reading

gal

Don't know your gallons? Use the pool volume calculator.

ppm

FC from your test kit, not total chlorine.

ppm

CDC: at least 1 ppm, 2 ppm with stabilizer, at most 10.

Product

The strength is on the label; 73% cal-hypo lists 70% available chlorine, which is what we dose on. Pool "liquid chlorine" and "chlorinating liquid" are the same thing.

How much to add

Updates as you type
36.9fl oz

of liquid chlorine 12.5% to take 18,000 gal from 1 ppm to 3 ppm free chlorine

Add 36.9 fl oz: 1 jug of liquid chlorine 12.5% (1 gal each).

  • 1 jug of liquid chlorine 12.5% (1 gal each)$4–$10
    36.9 fl oz needed; about 91.1 fl oz left over for next time.

    Typical price (estimate, checked Oct 2026): $4.00–$10.00 per 1 gal jug of liquid pool chlorine

    1 jug × $4.00–$10.00 = $4–$10Estimate
Project total (estimate where no price is entered)$4–$10
Checked Oct 2026
  • Adds a little salt and raises pH briefly; pH settles back as the chlorine is used up.

Safety: Estimate only. Add chemicals to water, never water to chemicals. Never mix products. Add one product at a time with the pump running, and retest before adding more.

Targets: CDC Model Aquatic Health Code.

Show the math
Raise: 3 − 1 = 2 ppmLiquid chlorine 12.5%: 10.2 fl oz raises 10,000 gal by 1 ppm18,000 gal ÷ 10,000 × 2 ppm × 10.2 = 36.9 fl oz

How it works

The formula

chlorine needed (g) = gallons × 3.785 L × ppm increase ÷ 1,000
product = chlorine needed ÷ product strength

1 ppm is 1 milligram per liter. 10,000 gallons is 37,854 liters, so raising it by 1 ppm takes 37.9 g of chlorine. Each product carries a different share of it:

  • Liquid chlorine 12.5%: 10.2 fl oz per 10,000 gal per 1 ppm. Adds a little salt and raises pH briefly; pH settles back as the chlorine is used up.
  • Liquid chlorine 10%: 12.8 fl oz per 10,000 gal per 1 ppm. Adds a little salt and raises pH briefly; pH settles back as the chlorine is used up.
  • Bleach 8.25%: 14.7 fl oz per 10,000 gal per 1 ppm. Plain unscented bleach only: no splash-less, scented or "with cleaners" kinds. Same effect as liquid chlorine.
  • Bleach 6%: 20.7 fl oz per 10,000 gal per 1 ppm. Plain unscented bleach only: no splash-less, scented or "with cleaners" kinds. Same effect as liquid chlorine.
  • Cal-hypo 73%: 1.9 oz per 10,000 gal per 1 ppm. Raises calcium hardness and pH a little. Add it the way the label says (some say broadcast, some say pre-dissolve); undissolved granules can bleach vinyl.
  • Cal-hypo 65%: 2.1 oz per 10,000 gal per 1 ppm. Raises calcium hardness and pH a little. Add it the way the label says (some say broadcast, some say pre-dissolve); undissolved granules can bleach vinyl.
  • Dichlor 56%: 2.4 oz per 10,000 gal per 1 ppm. Adds stabilizer (CYA) every time you use it; switch to liquid chlorine once CYA reaches your target.

Assumptions

  • Liquid chlorine strength is "trade percent": grams of chlorine per 100 mL, the way pool chlorine is labeled.
  • Household bleach is labeled in percent sodium hypochlorite by weight; we convert with its density. 6% bleach takes 20.7 fl oz per 10,000 gal per ppm.
  • Bleach and liquid chlorine lose strength in storage, faster in heat. A jug that sat in a hot garage for a summer can be half strength; buy fresh and retest after adding.
  • The chlorine you need depends on your stabilizer (CYA): the more CYA, the higher the free chlorine you need. Many owners keep FC at about 7.5% of their CYA.

Worked example

18,000 gallon pool, 1 to 3 ppm, liquid chlorine 12.5%

  1. Raise: 3 − 1 = 2 ppm
  2. Per 10,000 gal per ppm: 10.2 fl oz
  3. 18,000 ÷ 10,000 × 2 × 10.2 fl oz = 36.9 fl oz
  4. That's about a third of a 1 gallon jug: $4–$10 for the jug at typical prices.

Chlorine to raise common pool sizes by 1 ppm

Amount of each product that raises free chlorine by 1 ppm
Pool sizeLiquid 12.5%Bleach 8.25%Cal-hypo 65%
5,000 gal5.1 fl oz7.3 fl oz1 oz
10,000 gal10.2 fl oz14.7 fl oz2.1 oz
15,000 gal15.4 fl oz22 fl oz3.1 oz
20,000 gal20.5 fl oz29.3 fl oz4.1 oz
25,000 gal25.6 fl oz36.7 fl oz5.1 oz
30,000 gal30.7 fl oz44 fl oz6.2 oz
40,000 gal41 fl oz58.7 fl oz8.2 oz

Multiply by the ppm you want to add. For 3 ppm in a 20,000 gal pool: 3 × 20.5 fl oz = 61.4 fl oz of 12.5% liquid chlorine.

Mistakes to avoid

  • Testing total chlorine instead of free chlorine. Only free chlorine sanitizes. Use a kit that reads FC and CC separately.
  • Mixing products. Never mix cal-hypo with trichlor or dichlor, or any chlorine with acid. Add one at a time, pump running, in different spots.
  • Old chlorine. Liquid chlorine and bleach weaken in storage. If the dose did less than expected, the jug is probably old.
  • Scented or splash-less bleach. They contain additives and less chlorine. Use plain, unscented bleach.
  • Dichlor every day. Each ppm of chlorine from dichlor adds 0.9 ppm of stabilizer, which builds up and makes chlorine weaker.

Questions people ask

How much liquid chlorine do I add to my pool?

10.2 fl oz of 12.5% liquid chlorine raises 10,000 gallons by 1 ppm. For a 18,000 gallon pool going from 1 to 3 ppm, add 36.9 fl oz.

Can I use household bleach in my pool?

Yes. Plain unscented bleach is the same chemical as pool liquid chlorine, just weaker. 8.25% bleach takes 14.7 fl oz per 10,000 gal per ppm. Skip scented, splash-less and "with cleaners" kinds.

What should my free chlorine be?

The CDC's Model Aquatic Health Code asks for at least 1 ppm, or 2 ppm if you use stabilizer, and no more than 10 ppm while people swim. With stabilizer you need more: about 7.5% of your CYA reading keeps algae away.

How long after adding chlorine can I swim?

With liquid chlorine or bleach, once it has mixed: about 30 minutes with the pump running, and free chlorine back in your normal range and within the product label's limit (some labels say 4 ppm or less; the CDC maximum is 10 ppm). Granules need to dissolve fully first. Retest before swimming.

Liquid chlorine, cal-hypo or dichlor: which should I use?

Liquid chlorine adds nothing else besides a little salt, so it is the usual daily choice. Cal-hypo adds calcium, fine if your water is soft. Dichlor adds stabilizer, handy for a new pool or small above-ground pools, but switch away once CYA reaches your target.