Pool salt formula
Pounds = (target ppm - current ppm) x gallons x 8.3454 / 1,000,000.
The worked example is a 15,000 gallon pool, 0 ppm now, 3,200 ppm target: 3,200 x 15,000 x 8.3454 / 1,000,000 = 400.6 lb. Ten 40 lb bags are 400 lb, which lands near 3,195 ppm. The page rounds the exact pounds up to whole 40 lb bags, so it shows 11 bags. Buy 10 if you would rather stop just under 3,200 ppm and retest.
Where the gallons come from
Use the pool's water volume, not the shell size on a brochure, if you have a recent measurement. A rectangle pool is length times width times average depth, in feet, times 7.48 to get US gallons. This page does not estimate that shape. If you only know the volume already, type it in.
After you add salt
Circulate, brush, and retest the next day. Salt does not evaporate with the water, so you mostly add salt when you drain or when rain and splash-out dilute the pool. Cyanuric acid, pH, and the chlorinator setting are separate adjustments.
Frequently asked questions
How much salt does a 15,000 gallon pool need?
From 0 ppm to 3,200 ppm, this formula gives 400.6 lb. That is 15,000 x 3,200 x 8.3454 / 1,000,000. Ten 40 lb bags are 400 lb, just under the target. Rounding up to whole bags is 11 bags.
What salt level should a saltwater pool be?
Many chlorine generators want about 2,700 to 3,400 ppm. The default target here is 3,200 ppm. Use the range printed in your chlorinator manual, not a generic number, if the two disagree.
How is pool salt calculated?
Pounds = (target ppm minus current ppm) x US gallons x 8.3454 / 1,000,000. The 8.3454 figure is the pounds of water in a gallon used for this ppm conversion. If the current reading is already above the target, add none.
Can I add all the salt at once?
Pour it in with the pump running and brush until it dissolves. Retest after 24 hours before adding more. Do not pile salt against a metal fitting, and do not turn the chlorinator on until the salt has dissolved.