Tub & Pool

Pool salt calculator

Updated November 10, 2026

Enter your pool's gallons, your current salt reading and your chlorinator's target, and this tells you how many pounds of salt to add. Don't know your gallons? Fill in the pool's shape and size and it works them out.

How much salt do I need?

gallons
ppm
ppm

3,200 ppm is Hayward AquaRite's optimal level. Change it to the figure in your own chlorinator's manual.

The formula

Pounds of salt = gallons × 8.34 × (target ppm − current ppm) ÷ 1,000,000

A gallon of water weighs 8.34 pounds, and one ppm (part per million) is one pound of salt in a million pounds of water. So you work out how many pounds of water you have, then multiply by the increase you want in ppm.

Example: a 20,000-gallon pool reading 2,400 ppm, aiming for 3,200 ppm. That's an 800 ppm increase. 20,000 × 8.34 × 800 ÷ 1,000,000 = 133 pounds, or just over three 40 lb bags.

As a check, Pentair's IntelliChlor guide has a table for reaching 3,400 ppm. It lists 284 pounds for 10,000 gallons starting from zero, and the formula gives 283.6. For 10,000 gallons starting at 2,800 ppm, the table says 50.12 pounds and the formula gives 50.0.

How to add the salt

Both Hayward and Pentair give similar steps in their manuals:

  1. Test the salt level first, with a test kit rather than only the chlorinator's display.
  2. With the pump running, pour the salt into the pool itself. Pentair says to pour it around the outer edge of the pool and not through the skimmer.
  3. Brush it around so it doesn't pile up on the bottom while it dissolves.
  4. Let the water circulate for 24 hours. Hayward notes the chlorinator's salt display can take that long to catch up.
  5. Test again before adding more.

Because the only way to take salt out is to drain and refill, it's sensible to add a bit less than the calculator says if you're unsure of your gallons, then top up after the retest.

New plaster? Don't add salt straight away. Hayward says to wait 10 to 14 days after new plaster, and Pentair says at least a month. Follow your pool builder's advice too.

Too much salt can cause problems of its own. Hayward says high salt can shut down the AquaRite and that salt starts to be tasted at about 3,500 to 4,000 ppm. Pentair warns that above 4,500 ppm it may corrode equipment and surrounding surfaces.

Salt alone isn't the whole picture

The salt is only there so the chlorinator can make chlorine. You still need to keep free chlorine, pH and stabilizer in range, and Hayward's manual says to check stabilizer (cyanuric acid) whenever you check salt. A test kit with a salt test covers all of it. If you add other chemicals, add them one at a time, following each label, and never mix them.

Common questions

What salt level should I aim for?

Whatever your chlorinator's manual says. Hayward's AquaRite manual gives 2,700 to 3,400 ppm, with 3,200 ppm as optimal. Pentair's IntelliChlor IC15 guide gives 3,000 to 4,500 ppm with 3,400 ppm as ideal, and recommends 3,000 to 3,500 ppm. Other makes differ, so check yours.

What kind of salt do I need?

Hayward's manual calls for sodium chloride that's more than 99% pure, and says not to use rock salt, salt with yellow prussiate of soda or anti-caking additives, or iodized salt. Bags sold for pools and salt chlorinators are the usual choice.

Does salt evaporate?

No. Hayward's manual says salt isn't lost to evaporation. It's lost when water leaves the pool: splash-out, backwashing, draining, or rain overflowing the pool.

I added too much salt. How do I get it out?

Hayward says the only way to lower salt is to partially drain the pool and refill with fresh water. If you enter a current reading above your target, the calculator shows roughly what share of the water you'd need to replace.

Can I trust my chlorinator's salt reading?

Use it as a guide, then confirm with a test. Pentair's guide says its salt sensor is accurate to within plus or minus 500 ppm and tells owners to always test salt before adding any.

Sources