Pool Salt Calculator
How many pounds and bags of salt to add to reach your chlorine generator's target, from a fresh fill or a low test reading, and how much water to replace if the salt is too high.
Salt (lb) = gallons × 8.34 × (target ppm − current ppm) ÷ 1,000,000. Raising 10,000 gallons by 100 ppm takes about 8.3 lb. Starting a 20,000 gallon pool from 0 to 3,200 ppm takes about 534 lb (14 bags of 40 lb).
Salt needed for a new salt pool (0 → 3,200 ppm)
| Pool gallons | Salt (lb) | 40 lb bags |
|---|---|---|
| 5,000 | 133 | 4 |
| 10,000 | 267 | 7 |
| 15,000 | 400 | 11 |
| 20,000 | 534 | 14 |
| 25,000 | 667 | 17 |
| 30,000 | 801 | 21 |
| 40,000 | 1,068 | 27 |
How to add salt
- Test salt with strips or a meter; generator readouts drift.
- Turn the generator off, run the pump, and pour salt around the deep end.
- Brush undissolved salt toward the drain; wait 24 hours, then retest.
- Add the last quarter only after the retest, because salt is easy to add and hard to remove.
Frequently asked questions
How much salt do I need for my pool?
Multiply gallons × 8.34 × the ppm you need to add, then divide by 1,000,000. Most chlorine generators want about 2,700–3,400 ppm, with 3,200 a common ideal. A new 15,000 gallon pool needs about 400 lb.
How many bags of salt for a 20,000 gallon pool?
About 14 bags of 40 lb to go from 0 to 3,200 ppm. To raise it by 500 ppm, about 83 lb, or 3 bags.
What happens if there is too much salt in the pool?
Very high salt can trigger a generator's high-salt shutdown and taste noticeably salty. Salt does not evaporate, so the only fix is to drain part of the water and refill; the calculator shows what percentage to replace.
What kind of salt should I use?
At least 99% pure sodium chloride sold for pools, without anti-caking agents or iodine. Pool salt dissolves quickly and doesn't stain.
How often do you add salt to a pool?
Only when testing shows it is low, typically after heavy rain, backwashing or splash-out. Salt isn't used up by chlorination, so a well-kept pool may need only a few bags a season.
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Formula: 1 gallon of water weighs 8.34 lb, and ppm is parts per million by weight. Target ranges follow salt chlorine generator manuals, such as Hayward AquaRite (2,700–3,400 ppm, ideal 3,200); always use your generator's range. Volume formulas use 7.48 gallons per cubic foot; round and oval pools use π/4 × 7.48 ≈ 5.9; kidney pools use the industry approximation (A + B) × length × depth × 3.38. Real pools with steps, benches and sloped floors vary by a few percent.