Pool Salt Calculator

Background.

A pool salt calculator should begin with the generator manual, not with a universal salinity target. Hayward's AquaRite manual gives an ideal range of 2,700 to 3,400 parts per million and names 3,200 ppm as optimal. Pentair's December 2025 IntelliChlor Plus and LT guide names 3,600 ppm as ideal, warns when the reading is below 3,000 ppm or above 4,500 ppm, and shuts the cell down below 2,600 ppm. Pentair's 2017 IC15 table instead calculates additions to 3,400 ppm. A difference of 400 ppm is 12.5% of Hayward's target, so treating every salt system as though it wanted the same number can mean buying several unnecessary bags. Select the exact system you own, or copy the target from your own manual into custom mode.

The arithmetic uses concentration directly. Pool salinity in ppm is treated as milligrams of sodium chloride per litre of water. The missing concentration is the selected target minus the salinity measured now. Multiplying that difference by the pool volume in litres gives milligrams of pure salt; converting milligrams to kilograms and then kilograms to pounds produces the mass to add. The purity entry matters because a 99.5% sodium chloride product contains slightly less salt per bag than a hypothetical 100% product. Whole bags are rounded up only after the exact required mass is known, so the page shows both the precise pounds and the practical number of bags to buy.

Do not add the calculated amount from an unchecked cell reading. Pentair's older IC15 guide states that its salt sensor reading is within plus or minus 500 ppm, and both manufacturers tell owners to verify readings after circulation. Confirm a large correction with a separate reliable salinity test, add salt around the pool perimeter rather than through the skimmer, brush piles off the floor, circulate for 24 hours, and retest before adding more. Overshooting is not corrected by a chemical: Hayward says the only way to lower salt concentration is to drain part of the pool and replace it with fresh water. When the reading is above target, this page therefore reports the dilution volume instead of a negative amount of salt.

Salt type and surface age are scope-changing limits, so they appear beside the result as well as here. Hayward specifies sodium chloride greater than 99% pure and excludes rock salt, iodized salt, salt with anti-caking additives, and salt containing yellow prussiate of soda. Its manual says to wait 10 to 14 days before salting new plaster; Pentair's IC15 guide says at least one month. Follow the surface manufacturer's instructions for your pool, because the generator manufacturer does not control the plaster or liner warranty.

This calculator sizes sodium chloride only. It does not decide whether free chlorine is adequate, balance pH, alkalinity, calcium hardness or cyanuric acid, select generator output, or replace the instructions for electrical installation and bonding. A salt cell makes chlorine only while water is flowing and the cell is operating. If the result says the cell is shut down, use the sanitation method directed by your pool professional while the salt dissolves and the system is restored.

What is pool salt calculator?

Salinity is the concentration of dissolved salt in the pool water. Salt chlorine generators use sodium chloride already dissolved in the water to produce chlorine by electrolysis, then the chlorine ultimately returns to chloride and the cycle continues. Salt is therefore lost mainly when salted water leaves through backwashing, splash-out, rain overflow or deliberate draining, not when pure water evaporates.

A target ppm is an equipment specification. It is not a generic water-quality target and it is not transferable between every generator. The system selector carries the target, warning edge and shutdown edge from a named manual edition. Custom mode deliberately has no manufacturer band; it compares only with the target you enter.

The dilution result follows conservation of dissolved salt. If a 15,000-gallon pool is at 4,000 ppm and must return to 3,200 ppm, the salt mass must fall to 3,200 / 4,000, or 80%, of its current amount. Replacing 20% of the salted water with fresh water achieves that idealized result. Test the replacement water and retest after circulation because real fill water may already contain salt.

How to use this calculator.

1. 01Read the model label on the installed salt chlorine generator and select the matching manual edition. If it is not listed, select custom and enter the target from your own manual.
2. 02Enter the pool's water volume in US gallons or litres. Use the Pool Volume Calculator first if the volume is not known.
3. 03Enter a current salinity reading from a reliable test. Confirm a large correction independently rather than relying only on the cell display.
4. 04Copy the sodium chloride purity and bag weight from the product label, then enter the current price per bag.
5. 05Read the exact pounds, kilograms and whole bag count. Add gradually, circulate for 24 hours and retest before using any remainder.
6. 06If the pool is already above target, follow the dilution result and the manufacturer's draining guidance instead of adding any product.

The formula.

Let V be pool volume in litres, C now be the measured salinity, C target be the selected manual target, and p be the sodium chloride purity as a percent. The positive concentration deficit is ΔC = max(0, C target − C now). Because one ppm in this context is one milligram per litre, pure salt kilograms equal V × ΔC ÷ 1,000,000. Bagged salt kilograms equal that pure mass × 100 ÷ p, and pounds equal kilograms ÷ 0.45359237. US gallons are converted with the exact NIST value 3.785411784 litres per gallon.

The number of bags is ceil(salt pounds ÷ bag pounds). That ceiling is the only intermediate rounding: it represents a physical purchase, not a display choice. Every other arithmetic result is retained in Decimal precision and rounded once at the return boundary to ten decimal places. Cost is whole bags multiplied by price per bag.

When C now is greater than C target, no salt is added. The idealized fraction of pool water to replace is 1 − C target ÷ C now. The displayed replacement volume is V pool × that fraction, returned in the same gallons-or-litres unit the user entered.

The status output classifies the unrounded current reading. Hayward edges are shutdown below 2,400 ppm, ideal from 2,700 through 3,400 ppm. Pentair Plus/LT edges are shutdown below 2,600 ppm, warning below 3,000 ppm and high above 4,500 ppm. The 2017 IC15 mode uses shutdown below 2,600 ppm and the guide's green 2,800 through 4,500 ppm band. Custom mode has no published classification.

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.