How to use the pool salt calculator
- Enter the pool volume and choose gallons or liters.
- Enter the salt level now from a test, and the level you want from your salt system manual. The 3,200 ppm shown is an example.
- Open More options to enter the purity printed on the salt bag and the bag size.
- Read the pounds of salt to add, the number of bags and how much one bag raises the level.
Formula
pounds of water = gallons x 8.3454
salt in pounds = pounds of water x (target ppm - current ppm) / 1,000,000 / purity
bags = salt / bag size, rounded up
ppm per bag = bag size x purity / pounds of water x 1,000,000
One ppm of salt is one pound of salt per million pounds of water. A gallon of water weighs 8.3454 pounds at 1 kilogram per liter.
A 15,000 gallon pool
The water weighs 15,000 x 8.3454 = 125,181 pounds. To raise it from 400 to 3,200 ppm is 2,800 ppm, so the salt is 125,181 x 2,800 / 1,000,000 = 350.5 pounds of pure salt. With 99.8% salt that is 351.2 pounds, or 159.3 kilograms, which is 9 bags of 40 pounds. One bag raises the level by about 318.9 ppm.
A 60,000 liter pool is 15,850.3 gallons. Raising it from 0 to 3,000 ppm with pure salt takes 396.8 pounds. A 20,000 gallon pool from 250 to 4,000 ppm needs 625.9 pounds, or 13 bags of 50 pounds.
Test first, then add in steps
Measure the current level with a reliable test, since test strips and meters can disagree. Tap water, some chemicals and old salt all add to the reading. Add salt in stages, brush it so it dissolves, run the pump and wait before you test again.
A pool that is already at or above the target needs no salt. If the level is too high, the usual fix is to drain some water and refill, which is outside what this page calculates.
Why the volume matters
The answer scales directly with the volume, so a wrong volume gives a wrong amount. If you do not know the volume, estimate it with the Pool Volume Calculator. Salt adds a very small amount to the volume, which the page ignores. To see the salt as an amount of substance, the Moles to Grams Calculator converts pounds of sodium chloride to moles, at 58.44 grams per mole.
Related pool and water tools
Plan sanitizer with the Pool Chlorine Calculator, find the weight of salt for a fish tank with the Aquarium Salt Calculator, and find the volume of any tank with the Tank Volume Calculator.
Assumptions and limits
- The pool volume and the current salt level are accurate.
- The target is a value you choose from your equipment manual, not a standard set by this page.
- Salt dissolves fully and evenly, and its added volume is ignored.
- Purity comes from the bag and affects only the weight of salt needed.
Frequently asked questions
How much salt do I add to a pool?
Multiply the pounds of water by the increase in ppm divided by one million, then divide by the purity. A 15,000 gallon pool raised by 2,800 ppm with 99.8% salt needs about 351 pounds.
What does ppm mean for pool salt?
It means parts per million by weight, or pounds of salt per million pounds of water. 3,200 ppm is about 3.2 pounds of salt for every 1,000 pounds of water.
How many bags of salt is that?
Divide the pounds of salt by the bag size and round up. 351 pounds in bags of 40 pounds is 9 bags.
What target level should I use?
Use the range given in the manual for your salt system, since equipment differs. The 3,200 ppm on the page is only an example.