Pool Salt Calculator: How Much Salt Do I Add?

Pounds of salt to add = (target ppm − current ppm) × pool gallons × 8.34 ÷ 1,000,000. The target depends on your chlorinator: Hayward calls 3,200 ppm optimal for its AquaRite,¹ while Pentair’s IntelliChlor guide recommends 3,600 ppm.² A new 30,000-gallon pool needs about 800 lb, or 20 bags of 40 lb, to reach 3,200 ppm.

How many bags of salt for your pool size

The table shows the total salt needed to bring fresh water with no salt in it up to each brand’s ideal. Our formula gives the same pounds as both manufacturers’ own charts: Hayward’s within 1 lb at every size we checked,¹ and Pentair’s within 0.1%.² The 8.34 is the weight of one US gallon of water in pounds.³ Many calculators divide by 120,000 instead, which is the same rule rounded: 1,000,000 ÷ 8.34 is about 119,900.

Most pools aren’t at zero. Both manuals say to test before adding anything, because water that has been chlorinated for a while already holds some salt.^1,2 If you don’t know your gallons, the pool volume calculator works them out from length, width and depth and saves the number for this page.

Which salt level to aim for

Use the number in your own chlorinator’s manual. The cell turns salt into chlorine, and each brand sets the range its cell works in. The manuals of two major brands don’t agree, which is why a single “ideal” figure can be wrong for your pool.

Hayward’s figures come from its AquaRite owner’s manual.¹ Pentair’s come from the IntelliChlor installation and user’s guide.² Pentair’s two-page quick-start sheet gives 3,200–3,400 ppm instead,⁴ so if you own an IntelliChlor, go by the full guide for your model. The calculator offers 3,000, 3,200, 3,400 and 3,600 ppm.

Test the salt before you add any

A reading off by a few hundred ppm can mean a bag too many, and extra salt can only come out by draining. Pentair notes that salt readings differ between test strips, electronic testers and titration, and rates its own cell’s sensor at ±500 ppm.²

• Use two methods. Pentair suggests a hand-held meter calibrated for sodium chloride, and checking the cell’s reading against a separate test after you add salt.²
• Know what the display shows. Hayward’s salt display is an average. Its Instant Salinity reading shows the level at that moment, so the main display can trail behind for a day after you add salt.¹
• Get big doses checked. Before adding a large amount, Hayward advises having the salt level checked professionally.¹

How to add pool salt

1. 1

   Buy the right salt

   Use plain sodium chloride: Hayward asks for more than 99% pure,¹ Pentair at least 99.8%, food-quality and non-iodized.² Skip rock salt, iodized salt, salt with anti-caking agents (yellow prussiate of soda), and calcium or potassium chloride. Pellets work but dissolve more slowly.^1,2

2. 2

   Wait if the plaster is new

   Hayward says to wait 10–14 days on a new plaster pool;¹ Pentair says at least one month.² Follow your cell’s manual and the plaster maker’s advice.

3. 3

   Spread it around the pool

   With the pump running, pour the salt around the edge of the pool, not into the skimmer: Pentair warns that salt there can clog the filter and damage equipment.² Brush it so it doesn’t pile up on the floor.¹

4. 4

   Circulate for 24 hours

   Run the filter pump for 24 hours, drawing from the main drain if you have one, so the salt spreads evenly.¹

5. 5

   Retest, then adjust

   Take the next reading only after that 24-hour mix.² For outdoor pools, check stabilizer (cyanuric acid) at the same time: Hayward says the two usually drop together.¹ Our guide to ideal pool chemical levels covers chlorine, pH and the rest.

Where the salt goes, and how much rain takes

Salt chlorinators recycle the salt: it becomes chlorine, then turns back into salt. You lose salt only when salty water leaves the pool, through splashing, backwashing, or draining after rain.¹

Salt is not lost due to evaporation.

Rain is different. If the level rises and you pump the extra off, salt goes with it. The salt left is your average depth divided by your depth plus the rain you pump off, so one inch of rain removes about 1/61 of the salt in a pool averaging 5 ft deep (60 inches).

To see how much this varies across the country, we took NOAA’s 1991–2020 monthly rainfall normals for the weather station nearest each of 40,904 US ZIP codes and found each one’s wettest month from May to September.⁵ The median wettest swim month brings 4.7 inches. If all of it were pumped off a 5-ft pool, salt would fall by up to 240 ppm. May is the wettest swim month in 36% of ZIP codes and June in 28%.

These are ceilings, not forecasts. In a hot month, evaporation takes back part of the rain before you ever reach for the pump, and a solid cover keeps rain out of the water. Still, the pattern is useful. In Phoenix or Las Vegas, salt drops mostly through splashing and backwashing. In Tampa, Orlando or Houston, test after every big storm in the rainy season. Save your ZIP code and this page shows your own wettest month under the result.

If the salt level is too high

Salt can’t be filtered or treated out. The only way to lower it is to drain part of the pool and refill with fresh water.¹ The share to drain is (current − target) ÷ current: to bring 4,000 ppm down to 3,200 ppm, replace about 20% of the water. The calculator does this automatically when your reading is above the target.

Working in liters and kilograms

In metric the math is simpler, because one liter of water weighs about one kilogram.³ Kilograms of salt = (target ppm − current ppm) × liters ÷ 1,000,000. A 50,000-liter pool raised from 2,800 to 3,200 ppm needs 20 kg. Some cells can show salt in grams per liter instead: Hayward’s display reads 3.20 for 3,200 ppm in metric mode.¹

How this calculator works

The calculator uses the formula above, with 8.34 lb per gallon. It assumes the salt is pure sodium chloride and fully dissolved. The bag count rounds to a practical fraction of a bag, so pour slightly less and top up after retesting rather than overshooting. The rain line uses the depth you saved in the volume calculator, or 5 ft if you didn’t. Every constant and rule is listed on our methodology page.