Pool Salt Calculator
Work out how many pounds of salt to add to reach your target salinity from your current level.
Salt chlorine generators usually want around 3,000 to 3,400 ppm — check your unit. The math is gallons times the ppm gap times 8.34, divided by a million. You can only add salt, so if you're already above target the only fix is to drain and refill with fresh water.
How it works
A saltwater pool's chlorine generator needs a steady salt level — usually around 3,000 to 3,400 ppm — to make chlorine from the salt already in the water. When that level drifts low, you top it up.
The formula is gallons times the gap between your target and current salinity, times 8.34 (the pounds in a gallon of water), divided by a million. That gives the pounds of salt to dissolve in.
Going from 0 to 3,200 ppm in a 15,000-gallon pool works out to about 400 pounds, or ten 40-pound bags. Salt only comes out by draining and refilling, so if you overshoot you can't just remove it — add conservatively and retest.
Frequently asked questions
What salt level should I aim for?
Most salt chlorine generators want somewhere between 3,000 and 3,400 ppm, but check your unit's manual — running too low makes weak chlorine and running too high can trip a fault or corrode fittings.
What kind of salt do I use?
Pure, non-iodized sodium chloride labeled for pool or water-softener use, ideally 99% or higher purity. Avoid salt with anti-caking agents or iodine, which can stain or cloud the water.
How long until my reading is accurate?
Salt dissolves slowly. Broadcast it over the pool, brush it around, and run the pump for 24 hours before testing so the water is fully mixed and the reading is real.