Pool salt calculator

How many bags to add to reach the level your salt cell wants, and how much to drain if you overshot.

In short: Pounds of salt = gallons × (target ppm − current ppm) × 0.00000834. Bringing 10,000 gallons of fresh water to 3,200 ppm takes about 267 lb, or seven 40 lb bags.

Formulas reviewed November 1, 2026 · How we calculate

Your pool

400 lb of salt

That's 10 bags of 40 lb. Add about half, brush it around, run the pump 24 hours, then test again before adding the rest.

40 lb bags
10
Increase
3,200 ppm
Pool size
15,000 gal

What to add

  1. 400 lbPool salt (sodium chloride, 99%+ pure, no iodine or anti-caking agents)

What would change your result

  • Aiming for 3,000 ppm instead uses 25 lb less salt, if your cell's range allows it.
  • Salt pools hold chlorine best with stabilizer (CYA) at 60–80 ppm. Check yours and get the dose.Open
  • Salt cells push pH up, so most salt pools need acid every week or two.Read

Turn the salt cell off while the salt dissolves, and keep it off until the reading is stable.

How much salt does a pool need? Chart by pool size

Pounds of salt and 40 lb bags to reach 3,200 ppm, from fresh water or from a typical low reading.

Pool sizeFrom 0 to 3,200 ppmFrom 2,500 to 3,200 ppm
10,000 gal267 lb (7 bags)58 lb (2 bags)
15,000 gal400 lb (10 bags)88 lb (3 bags)
20,000 gal534 lb (14 bags)117 lb (3 bags)
25,000 gal667 lb (17 bags)146 lb (4 bags)
30,000 gal801 lb (20 bags)175 lb (5 bags)

Getting it right

A salt water pool under a white pergola in Florida.
Photo: Whoisjohngalt, CC BY-SA 4.0

Read the salt level twice. Salt cells estimate salt from current flow, and a scaled or aging cell often reads low. Before adding hundreds of pounds, confirm with a salt test strip.

Add it in the shallow end, with the pump running. Pour it around the perimeter, brush it toward the main drain, and turn the cell off until the salt has dissolved, usually about 24 hours.

Add half, then test. Overshooting is easy to do and only fixed by draining, so the calculator's two-step approach is worth the extra day.

Rain and splash-out lower salt; evaporation doesn't. After a wet week, retest before adding more chlorine-producing time to the cell.

Key facts

  • It takes about 8.3 lb of salt to raise 1,000 gallons by 1,000 ppm.
  • Most salt chlorine generators run best between 2,700 and 3,400 ppm; the exact range is in your cell’s manual.
  • Salt does not evaporate or get used up. Rain, splash-out and backwashing are what lower it.

How it's calculated

Pounds of salt = pool gallons × salt increase in ppm × 8.34 ÷ 1,000,000.

The 8.34 is the weight of one gallon of water in pounds, and ppm means pounds per million pounds of water. Bags are rounded up.

If the salt is already too high, the only fix is dilution. The share of water to replace is 1 − target ÷ current.

Questions people ask

How much salt do I need for a 15,000-gallon pool?

From zero to 3,200 ppm, about 400 lb, or ten 40 lb bags. If the pool already reads 2,500 ppm, you only need about 88 lb, or three bags.

How many bags of salt for a 20,000-gallon pool?

From fresh water to 3,200 ppm, about 534 lb: fourteen 40 lb bags. Starting from 2,500 ppm, about 117 lb, or three bags.

How long does pool salt take to dissolve?

With the pump running and some brushing, usually 24 hours. Test after that, not right away.

What happens if I add too much salt?

Most cells shut down or throw a high-salt warning, and the water can taste salty. Lower it by partly draining and refilling with fresh water.

Can I use water softener salt?

Only if the bag says it is pure sodium chloride with no additives. Avoid rock salt, iodized salt and salt with anti-caking agents or rust inhibitors.

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