Pool Salt Calculator: Pounds and Bags for Your Salt System

This calculator turns a salt reading into the pounds of salt to add and the whole bags to buy, aimed at the target of the salt chlorine generator you pick. It also shows where the salt level would end up if every bag went in, since salt is sold by the bag. You'll need the pool's volume in gallons; if you don't know it, start with the pool volume calculator.

Worked example: topping up a 15,000-gallon Hayward pool

Here is an example with the numbers the calculator opens with. A 15,000-gallon pool tests at 2,400 ppm of salt, the generator is a Hayward AquaRite, and the store sells 40-lb bags. Hayward's target is 3,200 ppm, so the pool is 800 ppm short.

• Salt to add is 100.1 lb.
• That rounds up to 3 bags of 40 lb, or 120 lb in all.
• With all three bags in, the pool sits at 3,359 ppm, which stays inside Hayward's range.

Each manual's target and range

The Salt chlorine generator menu fills in the target from each maker's manual. Pick Custom target if yours isn't listed, and type the figure from your own manual.

Hayward AquaRite. The manual says "The ideal salt level is between 2700-3400 ppm (parts per million) with 3200 ppm being optimal." The calculator aims for 3,200 ppm, and warns if the bags would take the pool above 3,400.

Pentair IntelliChlor. Pentair states that "3600 ppm of salt is recommended for optimum water condition." It also warns that "Low salt concentration below 2600 ppm will cause the unit to turn off", so the calculator flags a reading under 2,600 ppm when Pentair is picked. Its target is 3,600 ppm.

Jandy AquaPure. Jandy works in grams per liter: "3.0 to 3.5 gpl of salt is recommended for optimum water conditions." Its manual converts that with "1 gram per liter (GPL) = 1000 ppm (parts per million)", which makes the range 3,000 to 3,500 ppm. The calculator fills to 3,000 ppm, the level Jandy's own salt table uses. Jandy also has a shut-off point: "If salinity is below 2.0 gpl the system will automatically turn the electrolytic cell off until the salinity is raised above 2.0 gpl." A reading below 2,000 ppm gets a warning.

CircuPool CORE. CircuPool writes: "The ideal salt level for operation is about 3500 ppm (parts per million), and it is suggested to keep the salinity between 3000-4000 ppm." The calculator's target is 3,500 ppm.

The MAHC. The Model Aquatic Health Code, a public-pool code, doesn't set a salt figure of its own. It leaves the range to the maker: "The saline content of the POOL water shall be maintained in the required range specified by the manufacturer."

The formula

Pounds of salt = gallons × 8.345404 × ppm to add ÷ 1,000,000.

The constant comes from the units. One ppm of salt in water is one milligram per liter. NIST SP 811 gives a US gallon as 3.785412 liters and a pound as 453.5924 grams, so a million ppm across one gallon would weigh 3,785.412 grams, or 8.345404 lb. Salt-generator manuals round that to 8.34.

As a check, Pentair's salt table lists 300.43 lb for 10,000 gallons going from 0 to 3,600 ppm, and this formula gives the same 300.43. The legible cells in Hayward's, Jandy's and CircuPool's tables land within about a pound of it up to 20,000 gallons. The table below the calculator is this site's own arithmetic from the same formula, not a copy of any manual's chart.

Buying and adding salt

Hayward notes that pool salt is "usually available in 40-80 lb. bags", and adds that "It is important to use only sodium chloride (NaCl) salt that is greater than 99% pure." Pick your size under Bag size, or choose Custom and enter the weight printed on the bag. The calculator always rounds bags up, so check the level the whole bags would give before emptying the last one.

Both Hayward and CircuPool point out that "Salt is not lost due to evaporation." Salt leaves with water that is splashed out, backwashed or drained, so a top-up after heavy rain or a round of backwashing is the usual reason to reach for this calculator.

What this calculator doesn't cover

• Lowering salt. The only way down is to drain some water and refill with fresh, so there is no dose to work out.
• Spas and hot tubs. This page is for pools only.
• New plaster. Hayward's, Pentair's and CircuPool's manuals all ask you to wait before salting a new plaster pool. Hayward says "For new plaster pools, wait 10-14 days before adding salt to allow the plaster to cure." Pentair says "Wait at least ONE (1) MONTH after construction to allow plaster to cure before adding salt and operating IntelliChlor SCG." CircuPool says to "wait 30 days or longer if specified by your builder for plaster to cure before adding salt". Pentair also points you to the pool surface manufacturer's guidelines, so check those and your own generator's manual first.
• How fast to add it and how long to circulate. Follow your generator's manual for that, including whether to keep the cell off while the salt dissolves.

Record each salt reading in the pool chemistry log, so you can see how quickly your own pool loses salt between top-ups.