Pool Salt Calculator
Enter your volume, your current salt level and your target. The calculator gives you pounds, bags, and if you are above target, how much water you need to replace instead.
Check the reading before anything else
A reading above 6,000 ppm is more likely an instrument fault than salt in the water: a cell reporting wildly high is a known failure mode. Confirm it with a water test before you add or drain anything.
Salt systems infer salinity from conductivity rather than measuring salt. Get a water test before you dose. Which reading to trust
Enter your pool volume and current salt level.
You are in range. No salt needed.
Full dose
lb
× lb bags,
Add half now
lb
Add this much, wait 24 hours, retest
The full dose adds about ppm, taking you to about ppm.
If your pool is under about 8,000 gallons, weigh out partial bags.
You are above target. There is no chemical that removes salt: you replace water.
Water to replace
gal
of your pool, about inches off the surface
Show the working
How it works
Salt dosing is straightforward arithmetic. One pound of salt in 1,000 gallons of water raises salinity by about 120 ppm, because 1,000 gallons of water weighs roughly 8,345 pounds.
pounds of salt = (gallons × ppm increase) ÷ 120,000
A 40 lb bag therefore moves 10,000 gallons by about 480 ppm. Sanity-check any chart you find against that.
Going the other direction, there is no chemical that removes salt. You replace water:
fraction to replace = 1 − (target ppm ÷ current ppm)
Pick your target from your equipment, not from a round number
Most calculators default to 3,200 ppm. That is a reasonable middle, but your manufacturer’s window is the number that matters, and running below it makes your cell work harder for the same chlorine. Typical residential ranges fall between 2,700 and 3,400 ppm depending on the system. Check your manual, and aim for the middle of your window rather than the bottom, so a heavy rain does not drop you into a low-salt warning.
Before you trust the answer
Two inputs can wreck a perfectly correct calculation.
Your volume. If you are using a figure from a builder, a listing or the side of a box, it could be out by 20% or more, and your dose will be out by the same margin. The average depth trap is where most of that error comes from. Measure once properly and you will use the number for years.
Your current reading. If it came off your control panel, be careful. Salt systems infer salinity from conductivity rather than measuring salt, so scale, plate wear, cold water or the wrong cell model set in the menu all move the display with no salt moving. Get a water test before you dose. Which reading to trust walks through it.
Then do these two things
Add half, wait a day, retest. Salt needs time to dissolve and distribute. A reading two hours after pouring tells you nothing.
Brush it off the floor. Salt dumped in one spot stays there. This is the single reason behind nearly every “I added six bags and nothing happened” story, including the owner who put twelve bags into a pool they thought held 8,403 gallons and still read 500 ppm, whose actual problem was the volume figure.
If your pool is under about 8,000 gallons, weigh out partial bags. A full 40 lb bag in a 5,600 gallon pool is an 860 ppm jump, which is a lot to take back.
If you are already over target
Use the drain-down planner instead. It works out gallons to replace, inches off the surface, and what the partial drain does to your calcium hardness, cyanuric acid and alkalinity, which is the part that catches people out.
Worried your reading is the problem rather than your salt? The Salt Cell Protection Kit has the reconciliation decision tree, brand-specific target ranges, the cell health test and the cell-type audit that catches a panel configured for the wrong cell. $47.