Liquid chlorine calculator
For every 1,000 gallons, 1.28 fl oz of 10% liquid chlorine or 1.02 fl oz of 12.5% raises free chlorine (FC) by 1 ppm. An older, weaker jug needs more.
Always follow your product’s label directions. Pool and spa chlorine, bromine, shock and algaecides are EPA-registered pesticides: use products labeled for pool or spa use, and don’t swim or soak until levels are within the limit on your product’s label. If this page and a label disagree, the label wins.
| Pool size | Pool liquid chlorine 12.5% | Pool liquid chlorine 10% |
|---|---|---|
| 500 gal | 0.5 fl oz15 mL | 0.6 fl oz19 mL |
| 1,000 gal | 1.0 fl oz30 mL | 1.3 fl oz38 mL |
| 2,000 gal | 2.0 fl oz61 mL | 2.6 fl oz76 mL |
| 3,000 gal | 3.1 fl oz91 mL | 3.8 fl oz114 mL |
| 4,000 gal | 4.1 fl oz121 mL | 5.1 fl oz151 mL |
| 5,000 gal | 5.1 fl oz151 mL | 6.4 fl oz189 mL |
| 6,000 gal | 6.1 fl oz182 mL | 7.7 fl oz227 mL |
| 7,000 gal | 7.2 fl oz212 mL | 9.0 fl oz265 mL |
| 8,000 gal | 8.2 fl oz242 mL | 10 fl oz303 mL |
| 10,000 gal | 10 fl oz303 mL | 13 fl oz379 mL |
| 12,000 gal | 12 fl oz363 mL | 15 fl oz454 mL |
| 15,000 gal | 15 fl oz454 mL | 19 fl oz568 mL |
| 20,000 gal | 20 fl oz606 mL | 26 fl oz757 mL |
| 25,000 gal | 26 fl oz757 mL | 32 fl oz946 mL |
| 30,000 gal | 31 fl oz908 mL | 38 fl oz1.14 L |
| 40,000 gal | 41 fl oz1.21 L | 51 fl oz1.51 L |
Multiply by how many ppm you need. Example: FC 1 → 4 is +3 ppm. Each size links to its full dose chart.
On this page (10 sections)
Example: a 10,000-gallon pool needs 12.8 fl oz of 10% for each ppm. A jug that has lost a fifth of its strength needs a quarter more: 1.6 fl oz of "10%" chlorine per 1,000 gallons per ppm.
Calculator: gallons, current and target FC, jug strength
Enter your volume, your FC now, the level you want, and your stabilizer (CYA) so the calculator can check your target. Pick 10% or 12.5%, or type the exact percent from your jug.
The field most calculators skip is jug strength left. Liquid chlorine decays in storage, so a jug labeled 10% may deliver less. Leave it at 100% for a fresh jug. If you already know your jug is weaker than labeled (see the retest method below), enter the percent that is left: at 80%, the default 38 fl oz becomes 48 fl oz.
Fluid ounces per 1 ppm: chart for 1,000–40,000 gallons
The table above shows the amount for +1 ppm at each pool size. Multiply it by the ppm you need. Two shortcuts help when you are standing at the pool with a jug:
- One gallon of X% liquid chlorine raises a 10,000-gallon pool by X ppm. A gallon of 12.5% adds 12.5 ppm; a gallon of 10% adds 10 ppm. For 20,000 gallons, halve it.
- Per 1,000 gallons and 1 ppm: about 1 fl oz of 12.5%, or about 1.3 fl oz of 10%.
These work because pool chlorine is labeled in trade percent (explained next). They don't work for household bleach, which is labeled differently. For bleach, use the bleach calculator. For every product side by side, see how much chlorine to add.
10% vs 12.5%: what the label percent really means
Pool liquid chlorine is sodium hypochlorite sold in "trade percent": grams of available chlorine per liter, divided by 10. So 12.5% means 125 g of available chlorine in every liter, and 10% means 100 g. That is why 12.5% needs 20% less liquid for the same result: 10.24 fl oz instead of 12.8 fl oz per ppm in 10,000 gallons.
Sources don't fully agree on the conversion. Taylor's K-1005 tables use trade percent, and so do we. PHTA's fact sheet figures work out to about 3.5% more liquid per ppm (10.6 instead of 10.24 fl oz for 12.5% in 10,000 gallons). That gap is smaller than the error of a home test kit, so it rarely matters in practice. What does matter is price per ppm, not price per jug: a cheaper 10% jug can cost more per ppm than a 12.5% one. The chemical cost calculator does that comparison.
Can you pour liquid chlorine directly into the pool?
Yes. Liquid chlorine is made to go straight into the water. You don't need to dilute it. Pour it slowly, close to the surface, in front of a return jet with the pump running, so it mixes before it reaches the floor. Don't pour it into the skimmer if you use tablets or other chemicals in the skimmer or a feeder, and never into a bucket that held acid. Follow the directions on your jug's label.
How long does liquid chlorine take to work?
It starts working as soon as it mixes, because it is already dissolved. What takes time is mixing through the whole pool. Our calculators wait 30 minutes with the pump running before the next product, and a test 30 to 120 minutes after dosing tells you how much FC you really gained. If you dose in the evening, less of it is lost to sunlight.
Your jug loses strength: heat and age (PHTA data)
Sodium hypochlorite breaks down on its own, and heat speeds it up. According to PHTA, 12.5% sodium hypochlorite loses half its strength in about 180 days at 77 °F, but in about 48 days at 95 °F. A jug bought in spring and kept in a hot garage can be far weaker by August. At half strength, a gallon of "12.5%" in 10,000 gallons adds about 6.25 ppm, not 12.5.
How to find out what your jug really delivers:
- Test FC, then add a measured dose with the pump running.
- Retest after 30 to 120 minutes, with no rain and no swimmers in between.
- Divide the rise you measured by the rise the calculator predicted. A predicted +3 ppm and a measured +2.4 ppm means about 80% strength left.
Enter that percent in the "strength left" field for future doses. The Pooldex app does this step for you: it compares each dose with your next test and corrects the next dose automatically. To slow the loss, buy chlorine in amounts you will use within a few weeks and keep it in the shade.
Daily and weekly amounts: estimate from your own chlorine loss
No chart can tell you how much chlorine your pool uses per day. Sun, water temperature, stabilizer, rain, and swimmers change it. Measure it instead: test FC at the same time on consecutive days without adding anything in between, and note the average drop.
Example for 15,000 gallons with a loss of 2 ppm a day:
- 12.5% liquid chlorine: about 31 fl oz a day, or 1.7 gal (215 fl oz) a week.
- 10% liquid chlorine: about 38 fl oz a day, or 2.1 gal (269 fl oz) a week.
Daily small doses keep FC steadier than one big weekly dose. If your loss is much higher than expected with stabilizer in range, something is using up chlorine (often early algae). See chlorine not holding. The target range for your stabilizer is on pool chlorine levels. Using tablets instead? The chlorine tablets calculator turns the same daily loss into tablets per week.
Storage and handling safety
- Never mix liquid chlorine with acid, other chlorine products, or anything else. Mixing chlorine with acid releases toxic chlorine gas.
- Store jugs upright, capped, in a cool, shaded, ventilated place, away from acid and away from children and pets.
- Pour slowly, close to the water surface, in front of a return jet with the pump running. Rinse any drips off the deck with water.
- Wear gloves and eye protection. Liquid chlorine bleaches clothing on contact.
- Always follow the product label. It is a violation of federal law to use a pesticide product in a manner inconsistent with its labeling.
- Splashed in the eyes or swallowed: call Poison Control at 1-800-222-1222.
More in the pool chemical safety guide.
FAQ
How much liquid chlorine per day?
Multiply your daily chlorine loss in ppm by the amount per 1 ppm for your pool size. For 10,000 gallons losing 2 ppm a day, that is about 20 fl oz of 12.5% or 26 fl oz of 10% per day. Measure your own loss for a few days before settling on a number.
How much liquid chlorine to add to pool and how often?
Add enough to bring FC back to the top of your target range, as often as your pool needs to stay above the minimum. A pool that loses chlorine quickly in hot, sunny weather may need a dose every day. A covered or shaded pool may go longer. Your own test log is the only reliable guide. Dosing after sunset means less of it is lost to strong midday sun.
How much liquid chlorine to add to pool at startup?
New water has no stabilizer, and unprotected chlorine disappears fast in sunlight, so add stabilizer as well (see the stabilizer calculator). Then bring FC to about 3 ppm: for 15,000 gallons from 0 ppm, that is about 58 fl oz of 10% or 46 fl oz of 12.5% liquid chlorine. Test and top up daily until the reading holds.
Is liquid chlorine the same as shock?
Liquid chlorine is one of the most common ways to shock. "Shock" means raising chlorine well above normal for a while, and you can do it with liquid chlorine, cal-hypo (calcium hypochlorite), or dichlor. Products sold as "non-chlorine shock" (potassium monopersulfate) oxidize but do not sanitize. When you shock with liquid chlorine, follow the shock directions on its label, and don't swim until FC is back at or below the label's limit.
Sources
- PHTA fact sheet, Sodium hypochlorite (trade percent, decomposition data): phta.org
- Taylor Technologies, K-1005 treatment tables: PDF
- Orenda, Understanding labeled chlorine percentages: blog.orendatech.com
- CDC, Pool chemical injuries 2008–2017: archive.cdc.gov
- Poison Control (US): poison.org