Enter your pool volume, current salt reading, and your generator's target — get pounds of salt and how many bags to buy.
The pool salt formula
lbs of salt = (target ppm − current ppm) × gallons × 8.34 ÷ 1,000,000
Salinity in ppm is milligrams of salt per liter of water; the 8.34 converts through water's weight (8.34 lbs per gallon). The formula is exact — the uncertainty is in your volume estimate and your test kit, which is why the 80%-first approach exists.
A worked example
A fresh-filled 15,000-gallon pool (0 ppm) targeting 3,200 ppm needs 3,200 × 15,000 × 8.34 ÷ 1,000,000 ≈ 400 lbs — ten 40-lb bags. Add eight bags, circulate for a day, retest, and the last reading tells you whether the pool really is 15,000 gallons.
Salt keeps rising on its own?
Salt doesn't evaporate with water — it stays behind and concentrates. Rain and splash-out dilute it; topping up after evaporation doesn't. Over a season readings drift both ways, so retest monthly rather than assuming last spring's number.
Frequently asked questions
How much salt do I add to my pool?
About 8.3 lbs of pool salt raises salinity by 100 ppm in 10,000 gallons. To go from 0 to 3,200 ppm in a 15,000-gallon pool, that's roughly 400 lbs — ten 40-lb bags.
What salt level do salt water pools need?
Most salt water generators target 2,700–3,400 ppm, with 3,200 a common sweet spot — but check your specific cell's manual; running low makes the cell work harder and shortens its life.
What kind of salt should I use?
Plain sodium chloride pool salt, 99%+ pure, no additives. Never use iodized table salt or rock salt with anti-caking agents (yellow prussiate of soda), which can stain surfaces and cloud water.
Can I remove salt if I overshoot?
No chemical removes salt — the only fix is partial drain and refill with fresh water. That's why it's smart to add 80% of the calculated amount, let it circulate for 24 hours, retest, and top up.