Pool chlorine calculator

The exact amount of your chlorine to reach the level you want, and what else that chlorine adds to the water.

In short: For 10% liquid chlorine, 12.8 fl oz per 10,000 gallons raises free chlorine by 1 ppm. Raising a 15,000-gallon pool from 1 to 4 ppm takes about 58 fl oz.

Formulas reviewed November 1, 2026 · How we calculate

57.6 fl oz

of liquid chlorine 10% raises free chlorine from 1 to 4 ppm in 15,000 gallons.

Per 1 ppm: 19.2 fl oz
Increase: 3 ppm
Minimum for your CYA: 3 ppm

What to add

57.6 fl ozLiquid chlorine 10%

What would change your result

Tablets or liquid? See what each one adds to your water over a season.Read

Add chlorine in the evening with the pump running, and never mix it with acid or another chlorine product.

Next, for this pool

How much liquid chlorine to add: chart

Amount to raise free chlorine by 1 ppm. Multiply by the ppm you need.

Pool size	Liquid chlorine 10%	Liquid chlorine 12.5%	Cal-hypo 65%
10,000 gal	12.8 fl oz	10.2 fl oz	2.1 oz
15,000 gal	19.2 fl oz	15.4 fl oz	3.1 oz
20,000 gal	25.6 fl oz	20.5 fl oz	4.1 oz
25,000 gal	32 fl oz	25.6 fl oz	5.1 oz
30,000 gal	38.4 fl oz	30.7 fl oz	6.2 oz

Getting it right

Stacked jugs of liquid pool chlorine. — Photo: Maksym Kozlenko, CC BY-SA 4.0

Chlorine is the one number to check most often. Sun, heat and swimmers use it up every day, so most pools need a top-up every one or two days in summer.

Your target depends on stabilizer. The more cyanuric acid (CYA) in the water, the more chlorine it takes to keep algae away. Aim for at least 7.5% of your CYA level: 3 ppm with 40 ppm of stabilizer.

Add it in the evening, in front of a return jet with the pump running, so it mixes before the sun starts burning it off.

Liquid chlorine weakens on the shelf. A jug kept in summer heat can lose much of its strength in weeks. If doses stop working, buy fresh.

Key facts

1 gallon of 10% liquid chlorine raises 10,000 gallons by 10 ppm.
One pound of 65% cal-hypo raises 10,000 gallons by about 7.8 ppm.
Trichlor tablets add about 0.6 ppm of stabilizer for every 1 ppm of chlorine; dichlor adds about 0.9 ppm.

How it's calculated

Pounds of pure chlorine = gallons × ppm increase × 8.34 ÷ 1,000,000, divided by the product's strength (0.65 for 65% cal-hypo).

Liquid chlorine is labeled in trade percent, so 1 gallon of 10% raises 10,000 gallons by 10 ppm. The calculator converts that to fluid ounces.

The minimum target is 7.5% of your stabilizer level, a common rule for keeping algae from growing.

Questions people ask

How much liquid chlorine do I add to my pool?

For 10% liquid chlorine, about 12.8 fl oz per 10,000 gallons for each 1 ppm. To go from 1 to 4 ppm in a 15,000-gallon pool, that is about 58 fl oz.

What should my pool chlorine level be?

At least 7.5% of your stabilizer (CYA) level: about 3 ppm with 40 ppm of CYA, 6 ppm with 80 ppm. Many owners keep a little above that.

How often should I add chlorine to my pool?

Every day or two in summer, less in cool weather. Test before you add, and top up to your target.

Why is my chlorine always low?

Usually low stabilizer (sunlight burns unprotected chlorine), algae starting, or heavy use. Test CYA and check for algae.