About the Pool Salt Calculator
This pool salt calculator works out how much salt to add to a saltwater pool to reach the level your salt chlorine generator (SWG) needs. Enter the pool volume, your current salt reading and the target from your generator manual — most cells run at 2,700–3,400 ppm, with 3,200 ppm a common target — and it returns the pounds and kilograms of salt and the number of bags to buy.
It is useful when you first convert a pool to salt, after heavy rain or a partial drain, and when the cell reports low salt. If your reading is already above target, the calculator shows what share of the water to replace with fresh water instead, because salt can only be removed by dilution.
Use plain pool salt (at least 99% sodium chloride, no anti-caking agents or iodine). Salt test strips and generator readings can differ by a few hundred ppm, so add about three-quarters of the dose, brush it in, run the pump for 24 hours and retest before adding the rest.
With the default inputs, the salt to add is 401 lb. Change any value above to recalculate instantly.
How to use the pool salt calculator
- 1Enter your pool volume in gallons or liters.
- 2Test the current salt level with strips, a meter or your generator display.
- 3Enter the target from your chlorine generator manual.
- 4Pick your bag size and read off the pounds and bags needed.
- 5Add most of it, brush and circulate for 24 hours, then retest and top up.
Formula and method
Salt concentration in ppm is milligrams of salt per liter of water, so the salt needed is the ppm rise multiplied by the volume in liters, divided by one million to convert milligrams to kilograms. In US units this works out to about 8.345 lb per 1,000 ppm per 1,000 gallons, or 0.834 lb per 100 ppm per 1,000 gallons.
When the pool is above target, adding fresh water is the only fix. Replacing a fraction f of the water lowers salt from C to C × (1 − f), so f = (Current − Target) ÷ Current. The calculation assumes the salt is pure sodium chloride and fully dissolved.
- ppm
- Parts per million (mg of salt per liter)
- Liters
- Pool volume in liters (US gallons × 3.78541)
- f
- Fraction of water to drain and refill
Worked examples
New 15,000-gallon salt pool to 3,200 ppm
15,000 gallons is 56,781 liters. Raising it by 3,200 ppm takes 3,200 × 56,781 ÷ 1,000,000 ≈ 181.7 kg, or about 401 lb — just over ten 40 lb bags, so buy 11 and keep the spare for top-ups.
Top up 20,000 gallons from 2,600 to 3,200 ppm
A 600 ppm rise in 75,708 liters needs about 45.4 kg, which is roughly 100 lb of salt — two full 50 lb bags plus a little, so three bags.
50,000-liter pool reading 4,000 ppm, target 3,200
The pool is 800 ppm too salty, so no salt is needed. Replacing (4,000 − 3,200) ÷ 4,000 = 20% of the water — 10,000 liters, or about 2,642 US gallons — brings it back to 3,200 ppm.
Frequently asked questions
How much salt do I need for a 10,000 gallon pool?+
To go from fresh water to 3,200 ppm, a 10,000 gallon pool needs about 267 lb of salt — roughly seven 40 lb bags. Raising an existing pool by 500 ppm takes about 42 lb.
What salt level should a saltwater pool be?+
Most salt chlorine generators are designed for about 2,700–3,400 ppm, and many manufacturers recommend around 3,200 ppm. Always use the range printed in your own generator manual because cells differ.
What kind of salt should I use in a pool?+
Use pool-grade sodium chloride that is at least 99% pure, without iodine, yellow prussiate of soda or other anti-caking additives. Solar salt and pellet salt for water softeners also work if they are pure NaCl.
How long does pool salt take to dissolve?+
With the pump running and some brushing, granular pool salt usually dissolves within a few hours, but allow 24 hours of circulation before trusting a new salt reading or turning the generator back up.
How do I lower the salt level in my pool?+
Salt does not evaporate or get used up quickly, so the only way to lower it is to drain some water and refill with fresh water. The share to replace is (current − target) ÷ current.