Pool chlorine calculator
Not sure? Use the pool volume calculator.
Estimates for typical pool water. Always follow the product label, your state/local code and your certified pool operator. Add about three-quarters of a pH or alkalinity dose first, circulate, and re-test before adding the rest. Never mix chemicals or add acid and chlorine at the same time.
Quick answer
To raise free chlorine 1 ppm in 10,000 gallons, add about 10.2 fl oz of 12.5% liquid chlorine, 12.8 fl oz of 10% liquid chlorine, 2.1 oz of 65% cal-hypo, 1.5 oz of trichlor or 2.4 oz of dichlor. Multiply by the ppm increase you need and by your volume ÷ 10,000.
- Dose = ppm increase × gallons ÷ 10,000 × product amount per ppm.
- Trichlor adds ~0.6 ppm CYA and dichlor ~0.9 ppm CYA per 1 ppm chlorine.
- Cal-hypo adds ~0.7 ppm calcium hardness per 1 ppm chlorine.
- MAHC range: 1–10 ppm free chlorine in pools (2 ppm minimum with CYA); 3 ppm minimum in spas.
Chlorine dose chart
| Product | +1 ppm / 10,000 gal | +10 ppm / 10,000 gal | +18 ppm / 50,000 gal (2 → 20) |
|---|---|---|---|
| Liquid chlorine 12.5% | 10.2 fl oz | 102 fl oz (0.8 gal) | 7.2 gal |
| Liquid chlorine 10% | 12.8 fl oz | 1 gal | 9 gal |
| Bleach 6% | 21.3 fl oz | 1.7 gal | 15 gal |
| Cal-hypo 65% | 2.1 oz | 1.3 lb | 12 lb |
| Cal-hypo 73% | 1.8 oz | 1.1 lb | 10 lb |
| Trichlor 90% | 1.5 oz | 14.8 oz | Not recommended |
| Dichlor 56% | 2.4 oz | 1.5 lb | Not recommended |
Choosing a chlorine product
- Liquid chlorine (sodium hypochlorite) — the most common commercial choice for feed pumps. No CYA or calcium added; raises pH slightly at first and adds salt.
- Cal-hypo — dry, stores well, used in erosion feeders and for shock. Adds calcium hardness, so watch the LSI in hard-water areas.
- Trichlor — tablets for outdoor pools. Acidic and adds CYA fast; CYA builds up and slows chlorine, so test it monthly.
- Dichlor — fast-dissolving stabilized granular; adds even more CYA per ppm than trichlor.
How to calculate how much chlorine to add
- Test free chlorine. Use a DPD or FAS-DPD test to get the current free chlorine in ppm.
- Find the increase. Subtract current free chlorine from your target.
- Calculate. Multiply the increase by your volume ÷ 10,000 and by the product amount per ppm (10.2 fl oz for 12.5% liquid chlorine).
- Add and re-test. Add the chlorine with the pump running, circulate, re-test and record both readings in the pool log.
Frequently asked questions
How much liquid chlorine do I add to raise chlorine 1 ppm?
About 10.2 fl oz of 12.5% liquid chlorine per 10,000 gallons. A 50,000-gallon pool needs about 51 fl oz (0.4 gallon) per 1 ppm.
How much shock do I need for a commercial pool?
It depends on the goal. For breakpoint chlorination, raise free chlorine to 10 × combined chlorine. Use the breakpoint calculator and an unstabilized product such as liquid chlorine or cal-hypo.
Is 12.5% liquid chlorine the same as bleach?
Both are sodium hypochlorite. Pool liquid chlorine is usually 10–12.5% and household bleach about 6%, so you need roughly twice as much bleach. Use only plain, unscented bleach.
How long after adding chlorine can people swim?
Once free chlorine is within your code range (10 ppm maximum under the MAHC) and pH is in range. Re-test after the chlorine has circulated, typically 30 minutes to one turnover.
This page is an educational summary, not legal advice. Pool and spa codes differ by state and county and change over time — always confirm requirements with the health department that inspects your facility.