Pool Salt Calculator

Background.

A salt-water pool does not use up its salt. The chlorine generator splits dissolved sodium chloride to make chlorine, the chlorine does its work and ends up as chloride again, and the same salt goes round once more. Salinity falls only when salty water leaves the pool: backwashing, splash-out, rain that overflows, a partial drain. Evaporation removes water alone, so a hot dry spell concentrates the salt rather than diluting it.

The right level depends on the generator, and the manufacturers do not agree. Hayward's AquaRite manual calls 3,200 ppm optimal within an ideal 2,700–3,400 ppm. Pentair's December 2025 guide for the IntelliChlor Plus and LT names 3,600 ppm, warns below 3,000 and above 4,500, and stops the cell below 2,600. Pentair's 2017 IC15 guide works its salt table to 3,400 ppm. Filling a new pool to 3,600 rather than 3,200 takes 12.5% more salt, and for a top-up the gap is wider. Pick the unit you own, or copy the target from your own manual into the custom option.

The dose is plain arithmetic: litres of water times the shortfall in ppm gives milligrams of salt, corrected for the bag's purity and rounded up to whole bags. If the pool is already too salty, the answer becomes a volume of water to drain and replace, because nothing you can add will take salt back out.

Two cautions apply before you buy. A cell's built-in salt reading can be off by hundreds of ppm, so confirm a large correction with a separate test. And the right salt level does not mean the right chlorine level; free chlorine, pH, alkalinity, calcium hardness and stabiliser all need their own tests.

What is pool salt calculator?

Pool salinity is the amount of dissolved sodium chloride in the water, given in parts per million, which for pool water means milligrams per litre. At 3,200 ppm a pool is about a tenth as salty as the sea, which sits around 35,000 ppm, so it tastes faintly salty at most. The target is a setting for the chlorine generator rather than a health standard: the cell needs enough salt to work efficiently, and too much can trouble metal fittings and equipment.

How to use this calculator.

1. 01Select the generator named on your installed unit's label. If your model or manual edition is not listed, choose custom and enter the target printed in your own manual.
2. 02Enter the pool's actual water volume in US gallons or litres, not a figure from the brochure.
3. 03Enter the current salinity from a reliable test taken after the pump has been running, and double-check it independently if the correction is large.
4. 04Enter the purity, bag weight and price from the salt you plan to buy. Hayward asks for sodium chloride over 99% pure, with no iodine, anti-caking agents or yellow prussiate of soda, and not rock salt.
5. 05Pour the salt around the pool's edge, never through the skimmer, brush it off the floor, run the pump for 24 hours and retest before adding any final bag. If the pool is already above target, follow the drain-and-refill figure instead.

The formula.

Volume is first converted to litres, V = gallons × 3.785411784. The shortfall is ΔC = max(0, Cₜ − C₀), with Cₜ the target and C₀ the current reading. Since 1 ppm is 1 mg per litre, the pure salt needed is V × ΔC ÷ 1,000,000 kg. Dividing by the purity as a fraction gives the weight of bagged product, and dividing by 0.45359237 converts kilograms to pounds. Bags to buy are that weight divided by the bag weight, rounded up, and the cost is whole bags times the price. Each bag's effect is w × 0.45359237 × p/100 × 1,000,000 ÷ V ppm, which grows smaller as the pool gets bigger. When the pool is above target, the fraction of water to replace is f = 1 − Cₜ ÷ C₀, assuming the fresh water contains no salt. The status line compares the current reading with the selected manual's published levels; the custom option has no published levels, only your target.

A worked example.

Frequently asked questions.

References& sources.

1. [1]Hayward Industries, AquaRite Owner's Manual, document 092569 Rev B, Water Chemistry pages 4 and 16: 2,700–3,400 ppm ideal, 3,200 ppm optimal, below 2,400 ppm listed as a cause of little or no chlorine, salt purity and handling instructions, and partial drain/refill as the only lowering method. Retrieved 2026-07-31; open PDF.
2. [2]Pentair, IntelliChlor Plus and IntelliChlor LT Installation and Maintenance Guide, P/N 523854 Rev A, December 2025, Recommended Water Chemistry table and Control Panel Messages: 3,600 ppm ideal, warning below 3,000 and above 4,500 ppm, shutdown below 2,600 ppm. Retrieved 2026-07-31; open PDF.
3. [3]Pentair, IntelliChlor Salt Chlorine Generator Installation and User's Guide, document 522333.C, 27 June 2017, pages 7, 11 and 13–14: 2,800–4,500 ppm green range, shutdown below 2,600 ppm, ±500 ppm sensor statement, one-month plaster wait, and Table 1 additions to 3,400 ppm. Retrieved 2026-07-31; open PDF.
4. [4]National Institute of Standards and Technology, Handbook 44 — 2026, Appendix C, Units of Capacity or Volume — Liquid Measure: one US gallon equals 3.785411784 litres; SI mass definitions give one pound as 0.45359237 kilograms. Retrieved 2026-07-31; open PDF.