Pool salt calculator

Enter your pool's size, your current salt reading and the level your generator wants, and get the pounds of salt to add and how many bags that is.

Inputs

Not sure? Work it out with the pool volume calculator.

ppm

From a salt test strip, a salt meter or the readout on your generator. Tap water is usually 0–500 ppm.

Use the level in your generator’s manual. Makers differ by a few hundred ppm.

Pool salt usually comes in 40 lb bags (18 kg).

Salt to add

351lb

Raises 15,000 gal from 400 ppm to 3,200 ppm: 8.8 bags of 40 lb.

Add the salt with the pump running, brush it around, and run the pump about 24 hours before you retest.

Bags
8.8 × 40 lb
In kilograms
159 kg
Raise by
2,800 ppm
Target
3,200 ppm
Salt in the pool at target
401 lb
Salt level before and after
Salt400 → 3,200 ppm05,500NowAfter dosing
8.8 bags of 40 lb

To raise 15,000 gal of pool water from 400 ppm to 3,200 ppm you need about 351 lb of salt, 8.8 bags of 40 lb. The meter shows the salt level now and after adding it, against the 2,700 ppm–3,400 ppm range for this generator.

How it works

Salt is measured in parts per million, which for pool water is milligrams of salt per litre. So the salt to add is the ppm you need to raise, times the litres of water:

salt to add (kg) = (target − current) ppm × pool volume (L) ÷ 1,000,000
bags             = salt to add ÷ bag size
water to replace = 1 − target ÷ current    (only when the level is above target)
  • In pounds and gallons it is the pool-operator form: gallons × 8.34 × ppm change ÷ 1,000,000, which agrees with the litre form to within 0.3%.
  • The tables agree with it. Pentair’s kilograms are exactly litres × ppm ÷ 1,000,000. Hayward’s chart uses 8.33 pounds a gallon by weight, so it reads about 0.14% lower.
  • The meter shows where the salt is now and where it ends up, against the working range for your generator. The row of bags shows whole bags and how much of the last one you need.

Worked example

A 15,000 gallon pool reads 400 ppm and the generator wants 3,200 ppm:

  • Raise by: 3,200 − 400 = 2,800 ppm
  • Volume: 15,000 gal = 56,781 L
  • Salt: 2,800 × 56,781 ÷ 1,000,000 = 159 kg = 350.5 lb, which is 8.8 bags of 40 lb

Buy 9 bags, add 8 and most of the ninth, and retest the next day. Adding a little more than the last share does no harm as long as you stay under the top of your generator’s range.

Tips from the pool pad

  • Test, add, wait, test. Add about 90% of the calculated salt, run the pump for a day, and retest. It is much easier to add than to remove.
  • Do not use the cell’s readout alone. It is handy for trends, but check it against a separate salt meter once a season.
  • Watch stabilizer too. Hayward notes that salt and cyanuric acid tend to fall together, and suggests checking both at the same time.
  • Check your CYA. A saltwater pool usually runs higher stabilizer than a liquid-chlorine pool, and needs a higher free chlorine to match. The pool chemical and shock calculators have the chart.

FAQ

How much salt do I need to start a saltwater pool?

About 27 pounds for every 1,000 gallons to get from zero to 3,200 ppm, so roughly 267 lb for 10,000 gallons and 533 lb for 20,000. That is 7 and 14 bags of 40 lb. If your water already has some salt, test first; the calculator subtracts what is there.

What salt level should I aim for?

The level in your generator's manual. Hayward's AquaRite wants 3,200 ppm (2,700–3,400 is fine). Pentair's IntelliChlor guide lists 3,400 ppm in some editions and 3,600 in others, with 3,000–4,500 acceptable. If you are unsure, pick your brand above or enter your own target.

How do I lower the salt level?

Only by replacing water. Hayward says the only way is to partly drain and refill with fresh water. The calculator works out the share to replace: one minus the target divided by the current reading. At 4,000 ppm with a 3,200 ppm target that is 20% of the pool.

Why does my salt reading jump around?

Testers disagree. Pentair says its cell's built-in sensor is within about ±500 ppm, and strips, digital meters and titration each read a little differently. Hayward adds that the display may take 24 hours to catch up after you add salt, so run the pump, wait a day, then retest.

Can I add all the salt at once?

Yes, unlike most pool chemicals. Pour it in with the pump running and brush it around so it does not sit in a pile on the floor, then run the pump for about 24 hours with the suction on the main drain if you have one. Wait 10–14 days after plastering a new pool first.

Sources

  1. Aqua Rite Electronic Chlorine Generator manual (salt chart, page 4), Hayward. Ideal 2,700–3,400 ppm with 3,200 ppm optimal. "Pounds and (kg) of salt needed for 3200 ppm", e.g. 267 lb (121 kg) for 10,000 gal, 533 lb (242 kg) for 20,000 gal. Salt of 99%+ purity; the only way to lower salt is to drain and refill.
  2. IntelliChlor Install and User's Guide (IC15/20/40/60), Table 2, Pentair. Pounds (kg) of salt to reach 3,600 ppm by pool size and current salinity, e.g. 300.43 lb (136.27 kg) for 10,000 gal from 0 ppm. The cell shuts off below 2,600 ppm and high salt above 4,500 ppm risks corrosion. Other sections of the same guide give 3,400 ppm as the ideal.

Formula and sources last checked September 30, 2026. How we test formulas.

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