Saltwater Pool Salt Calculator

Saltwater pools are still chlorine pools. The salt cell electrolyzes salt (NaCl) into hypochlorous acid, the same active sanitizer as in any chlorine pool. The difference is where the chlorine comes from, not what it is.

The water is barely salty at all. A pool runs around 3,200 ppm against 35,000 ppm in the ocean, and your own tears sit near 9,000. So pool water is roughly a tenth as salty as the sea and a third as salty as crying, which is why most people notice nothing beyond the water feeling slightly softer.

There is no single correct salinity, and this is the page that takes that seriously. Pick your cell from the dropdown and the target comes from its manual rather than from a general rule:

The spread matters. A CompuPool cell wants 4,000 ppm, and 4,000 ppm in a Hayward pool is 600 above the top of its range and the sort of level that starts eating ladder bolts. Anyone quoting “the ideal salt level” without asking which cell you own is quoting the Hayward numbers, because AquaRite is the one most people have. The general-purpose pool salt calculator does exactly that, and it also counts bags and prices them, which this page does not.

The math. 1 lb of pool salt per 10,000 gallons raises salinity by ~12 ppm. Pool salt is just sodium chloride, the same as table salt minus the iodine and anti-caking agents. Mineral-grade pool salt (99%+ purity) is what you want.

To go from zero to 3,200 ppm:

• 10,000 gal pool: 3,200 / 12 × 1 lb = ~267 lb
• 20,000 gal pool: ~533 lb
• 30,000 gal pool: ~800 lb

That is a lot of bags. Most pool builders salt the pool at startup; you only need to top off after rain dilutes or partial drains. Salt does not evaporate, so once you are at target, you stay there for a long time.

Worked example. 20,000 gal pool, current salinity 2,200 ppm, target 3,200.

• Raise needed = 1,000 ppm
• Salt to add = 1 lb × (1000/12) × (20,000/10,000) = 167 lb (4 standard 40-lb bags, plus a partial bag)

Pour it across the deep end with the pump running. It dissolves in 24-48 hours. Brush the floor occasionally to break up any settled piles.

When salt is too high. The only fix is a partial drain and refill, because no chemical removes salt and it does not evaporate. The arithmetic is simple dilution: replacing a fraction f of the water leaves you at current × (1 − f), so to come down from 4,200 to 3,200 you replace 1 − 3200/4200, which is 24% of the pool. On 20,000 gallons that is 4,800 gallons out and back in. The calculator works that out for you when your current reading is above target.

Two cautions before you open a valve. Never drain a pool below the skimmer line without checking the hydrostatic relief valve, because a fibreglass or vinyl shell in wet ground can float. And if rain is forecast within a week, wait: two inches of rain drops salinity by 300 to 600 ppm on its own and costs you nothing.

Common mistake. Adding too much salt at once because the pool store reading was off. Pool store salt tests have a typical accuracy of +/- 200 ppm. Add in stages: go to two thirds of the calculated amount, retest in 48 hours, then top off if needed.