Pool Salt Calculator

Use the target range in the chlorine generator's manual. The calculator defaults to 3,200 ppm as an editable planning value, but systems use different operating ranges and warning thresholds. Test the current level before adding salt.

Test after draining, backwashing, overflow, leaks, or major water replacement and at the interval recommended by the system manufacturer. Add salt only when a reliable test is below that system's target range. Do not use a universal ppm threshold.

No. Salt does not evaporate, decay, or get consumed by the chlorinator. The cell uses electrolysis to convert dissolved salt into chlorine, and the chlorine converts back to salt as it sanitizes the water, so the salt itself recycles. The only way to lose salt is to lose water (splash-out, backwash, leaks, partial drains). That is why salt levels drift down slowly across a season rather than dropping after a busy weekend.

The calculator uses salt_lb = (gallons x ppm_increase) / 120,000. The constant comes from the units: 1 ppm equals 1 mg of salt per liter of water, 1 US gallon equals 3.785 liters, and 1 lb equals 453,592 mg. Combine those and 1 lb of salt raises 119,839 ppm-gallons by 1 ppm, which industry guides round to 120,000 for clean math. Some manuals quote 8.345 lb per million ppm-gallons; that is the same ratio expressed differently.

For dosing decisions, use a digital salt meter or a calibrated drop-titration kit. Salt test strips are convenient and fine for a quick sanity check, but they typically read in 400 to 500 ppm increments and can drift 200 to 500 ppm from the real value, which is enough to either under-salt the pool (chlorinator stops working) or over-salt it (cell wear and corrosion). Most chlorinators show a built-in salt reading on the control panel; cross-check that against a digital meter every few months because the in-cell sensor also drifts as the cell ages.