Pool Salt Calculator

About the Pool Salt Calculator

A saltwater pool uses a salt chlorine generator (SWG) to produce chlorine from dissolved salt. This calculator turns pool volume, a current salinity test, and the target from your equipment manual into three distinct numbers: pure-salt demand, the purity-adjusted product weight to add, and the number of whole packages to buy. Keeping those quantities separate matters because the last purchased bag is usually only partly needed.

How We Calculate Pool Salt Cost

First, required pure salt equals pool volume in gallons × the positive difference between target and current ppm ÷ 120,000. Second, pure-salt pounds are divided by the selected product's stated purity to produce the weight to add. Third, that product weight is divided by the package weight and rounded up only for purchasing. Cost follows whole bags purchased, while dosing follows the lower purity-adjusted weight; the unused purchased remainder is displayed and must not be added merely because the bag was bought.

Factors That Affect Pool Salt Cost

Factors that affect how much salt you need: pool volume (larger pools need proportionally more), current salt level (test before adding), target level (varies by generator model), salt purity (lower purity = slightly more needed), and recent water changes (rain, backwash, or refill dilutes existing salt).

Salt Needed for Each 1,000 ppm Increase

Pure-salt requirement before purity adjustment. Bag counts shown use the 99.8% 40-lb pool-salt profile; weigh the calculated product dose rather than adding all purchased product.

Source: Calculated from the model's salinity formula and 99.8% purity profile. Whole bags are a purchase quantity, not an instruction to add their full combined weight.

15,000-Gallon Pool: Salt to Reach 3,200 ppm

Pool-grade salt requirement at common tested starting levels. Always use the target specified by your chlorine generator.

Source: Calculated directly from this model for the 99.8% pool-salt profile. Product weight rounds to one decimal here; purchases round up separately.

Three pool-salt examples

Each example uses a 3,200 ppm target and the 99.8% 40-lb pool-salt profile. The cost range reflects $5–$10 per purchased bag.

Example 1 — 15,000 gallons currently at 1,500 ppm. Raising salinity by 1,700 ppm requires 212.5 lb of pure salt, or about 212.9 lb of the selected product. Buy six bags (240 lb) for $30–$60 with a $42 midpoint, but keep the roughly 27.1-lb purchase remainder out of the pool pending a retest.

Example 2 — the same pool tested at 500 ppm. The 2,700 ppm increase requires 337.5 pure-salt lb or about 338.2 product lb. Buy nine bags for $45–$90 with a $63 midpoint; the 360 lb purchased is not the dosing quantity.

Example 3 — 25,000 gallons currently at 1,000 ppm. The 2,200 ppm increase requires about 459.3 product lb, so 12 bags cost $60–$120 with an $84 midpoint. Measure the calculated product weight, follow the generator manual's staging procedure, and retest before the final addition.

Test first, then stop short of the target

Salt does not disappear through evaporation, so adding from an assumed starting level can overshoot. Verify pool volume, test salinity with a reliable method, and compare that reading with the chlorine generator's own display. If the readings disagree materially, resolve the test issue before adding hundreds of pounds.

Because bags are sold in whole units, the calculator shows a purchase quantity rather than instructing you to dump every bag at once. Add most of the calculated weight, circulate until dissolved, retest, and use only the remainder needed. Lowering excessive salinity normally requires removing pool water and replacing it with lower-salt water, making a cautious final dose cheaper than correcting an overshoot.

Choose salt by purity, not marketing name

Use high-purity sodium chloride that the chlorine-generator manufacturer permits. Pool salt is the straightforward choice. Additive-free solar salt can also work when its label confirms suitable purity and no iodine, anti-caking compounds, rust removers, fragrances, or other additives.

This calculator no longer presents rock salt as a normal option because mineral contamination and inconsistent purity work against precise dosing and can introduce staining or clouding risk. Product availability and generator requirements vary, so the equipment manual takes priority over a generic bag label.

Pool Salt by Pool Volume

National average at typical settings — use the calculator above for your exact inputs and location.

Sources

• • Chlorine-generator owner's manual — model-specific salt target, approved product, and startup procedure
• • Walmart — 40-lb Pool Salt Search Snapshot (accessed July 20, 2026)
• • Pool salinity mass conversion — approximately 1 lb of salt raises 120 gallons by 1,000 ppm

Costs are based on current industry ranges and vary by location and market conditions. See how we calculate costs — cost data last reviewed July 2026.