Pool Chlorine Calculator
Enter your pool volume, current and target free chlorine, and your product to see how much to add. The fields start with an example: a 15,000-gallon pool, raising chlorine from 1 to 3 ppm with 12.5% liquid chlorine (trade %).
Result: add about
of 12.5% liquid chlorine (trade %), about 908 mL. Raises free chlorine by 2.0 ppm in 15,000 gallons.
Chlorine needed: 113.6 g = 15,000 gal × 3.785 L × 2.0 mg/L ÷ 1,000.
Follow the product label.
Chemical safety: read before you add anything
- Never mix pool chemicals together, in or out of the water. Add each one separately.
- Never mix chlorine with acid. Never mix cal-hypo (calcium hypochlorite) with trichlor.
- Add acid to water. Never pour water into acid.
- Split large doses into smaller portions. A numeric per-dose limit is not verified.
- This result is an estimate. Follow the product label.
How Much Chlorine Do You Need?
1 ppm means 1 milligram of chlorine per liter of water. Multiply your gallons by 3.785 to get liters, then by the ppm increase you want, and divide by 1,000 to get grams of chlorine. Divide that by your product's strength to get the amount of product.
Product (g or mL) = gallons × 3.785 × ppm increase ÷ 1,000 ÷ strength
Example at trade percent, the default: 15,000 × 3.785 × 2.0 ÷ 1,000 = 113.6 g; ÷ 0.125 = 908 mL (30.7 fl oz, shown as 31 fl oz) of 12.5% liquid chlorine.
If that 12.5% is by weight, the Olin table lists about 14.1 trade percent, and the same 113.6 g is about 806 mL.
Pool liquid chlorine labels don't all use the same convention, so the calculator defaults to trade %.
CDC lists 1 to 4 ppm for a home pool. The code minimum is 1.0 ppm without cyanuric acid and 2.0 ppm with it, and the open-water maximum is 10.0 ppm. Source: CDC. Use of CDC information does not imply endorsement by CDC; available free at cdc.gov.
If the current reading and the target are equal, the dose is 0. If the target is lower, this page does not tell you how to bring chlorine down.
Pool Chlorine Calculator Results by Pool Volume
Amount of product to raise free chlorine by 1 ppm. Liquid columns are trade percent unless the heading says by weight. Cal-hypo (calcium hypochlorite) products labeled 73 percent are dosed at 70 percent, the EPA label minimum.
| Pool volumeGallons | Liquid 10% trade10% trade | Liquid 12.5% trade12.5% trade | Liquid 12.5% by weight12.5% weight | Cal-hypo at 70%70% cal-hypo |
|---|---|---|---|---|
| 5,000 gal | 6.4 fl oz | 5.1 fl oz | 4.5 fl oz | 1.0 oz |
| 10,000 gal | 13 fl oz | 10 fl oz | 9.1 fl oz | 1.9 oz |
| 15,000 gal | 19 fl oz | 15 fl oz | 14 fl oz | 2.9 oz |
| 20,000 gal | 26 fl oz | 20 fl oz | 18 fl oz | 3.8 oz |
| 30,000 gal | 38 fl oz | 31 fl oz | 27 fl oz | 5.7 oz |
| Pool volume | Dichlor dihydrate | Dichlor anhydrous | Trichlor | Bleach 6% by weight |
|---|---|---|---|---|
| 5,000 gal | 1.2 oz | 1.1 oz | 0.7 oz | 10 fl oz |
| 10,000 gal | 2.4 oz | 2.2 oz | 1.5 oz | 21 fl oz |
| 15,000 gal | 3.6 oz | 3.2 oz | 2.2 oz | 31 fl oz |
| 20,000 gal | 4.8 oz | 4.3 oz | 3.0 oz | 41 fl oz |
| 30,000 gal | 7.2 oz | 6.5 oz | 4.5 oz | 62 fl oz |
Dichlor dihydrate is specified at 55.0 to 57.1 percent available chlorine, and the dose uses 56 percent, inside that range. Dichlor anhydrous is specified at 62 percent or more, and the dose uses 62 percent. Each 1 ppm of free chlorine from dichlor also adds about 0.9 ppm of cyanuric acid. Per PHTA technical bulletin on dichlor. Per OxyChem ACL 56 sales specification. Per OxyChem ACL 60 sales specification.
Trichlor is specified at 90% or more, and the dose uses 90%. The cyanuric acid added by trichlor is not verified, so no ratio is shown. Household bleach at 6% by weight is dosed at about 6.2 trade %. Household bleach sold as 8.25% is weight percent, about 8.8 trade % (interpolated from the Olin conversion table). The 5.7% line is a CDC annex example of available chlorine, not a product recommendation. Per OxyChem ACL 90 PLUS sales specification. Source: CDC, 2023 Model Aquatic Health Code (MAHC), §Annex example. No CDC endorsement implied; available free at cdc.gov.
Common Mistakes With the Pool Chlorine Calculator
- Mixing chlorine with acid, or cal-hypo with trichlor. Add one chemical at a time.
- Assuming every 12.5% bottle is measured the same way. Pick trade % or weight %; trade % is the default.
- Ignoring a zero change. Equal readings mean a dose of 0, not a second scoop.
Use This Volume in Other Pool Calculators
Pool Chlorine Calculator FAQ
How much liquid chlorine raises 10,000 gallons by 1 ppm?
About 10 fl oz of 12.5% liquid chlorine (trade %), or about 9.1 fl oz if the label means weight %.
Can I add chlorine and pH down at the same time?
No. Add them separately and never mix them. A wait time between chemicals is not verified.
What free chlorine does CDC list for a home pool?
1 to 4 ppm. Source: CDC. Use of CDC information does not imply endorsement by CDC; available free at cdc.gov.