How this calculator works
Salt level is measured in parts per million (ppm), which is milligrams of salt per liter of water. A gallon of water weighs 8.34 pounds, so one ppm in a pool is 8.34 millionths of a pound of salt per gallon. Multiply the ppm you need to add by the gallons and by 8.34, and divide by a million.
Worked example: a 15,000 gallon pool at 400 ppm and a target of 3,200 ppm needs to rise by 2,800 ppm: 2,800 × 15,000 × 8.34 ÷ 1,000,000 = 350 pounds. That is 9 bags of 40 lb (8.8 rounded up). Starting from fresh water at 0 ppm it would be 400 pounds.
Pounds of salt to go from 0 ppm to 3,200 ppm
By pool size, with the number of 40 lb bags.
| Pool volume | Salt | 40 lb bags |
|---|---|---|
| 10,000 gallons | 267 lb | 7 |
| 12,000 gallons | 320 lb | 9 |
| 15,000 gallons | 400 lb | 11 |
| 20,000 gallons | 534 lb | 14 |
| 25,000 gallons | 667 lb | 17 |
| 30,000 gallons | 801 lb | 21 |
Tips before you buy
- Test the salt level with a reliable kit before and after you add salt. Strips are cheap but can be off by hundreds of ppm, and a digital salinity meter is more reliable.
- Add the salt around the edge of the pool with the pump running, then brush it across the floor. It takes a few hours to dissolve, and about a day to mix evenly.
- Do not add a lot of salt at once on top of an unknown level. Add in two steps if you are not sure of your pool volume, and retest.
- Salt is not used up like chlorine. You only add more to replace what is lost with splash-out, backwash and rain or when you drain the pool.
- Keep the pH and stabilizer (cyanuric acid) in range as well: the salt cell makes the chlorine, but it still needs balanced water.
Tools & materials for this project
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Frequently asked questions
How much salt do I need for a 15,000 gallon pool?
About 400 pounds (10 to 11 bags of 40 lb) to go from fresh water to 3,200 ppm. If the pool already has 400 ppm, about 350 pounds (9 bags).
How much salt do I need for a 20,000 gallon pool?
About 534 pounds from 0 ppm to 3,200 ppm, which is 14 bags of 40 lb.
What should the salt level be in a saltwater pool?
Most salt chlorine generators want 2,700 to 3,400 ppm, with 3,200 ppm typical. Check your cell's manual.
How do I lower the salt level in a pool?
You cannot remove salt. Drain some of the water and refill with fresh water. Draining 10% lowers the level by about 10%.
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Estimates only. Results assume standard materials and simple shapes. Supplier products vary, and the final call on quantity, structure and safety is yours. Check your local code and your supplier's guidance before ordering.