Pool salt calculator
This pool salt calculator works out how many gallons your pool holds, then how many pounds and 40 lb bags of salt raise it from your current reading to the target level, 3,200 ppm by default.
- Pool volume from rectangle, oval or round
- Pounds of salt and 40 lb bags
- Drain-and-refill amount if salt is too high
Last updated
How to use the pool salt calculator
- Pick your pool’s shape and enter its length and width (or diameter for a round pool) in feet.
- Enter the depth at the shallow and deep ends. The calculator averages them. For a pool with one depth, enter it twice. If you already know your gallons, choose “I know the gallons” instead.
- Test the water and enter the current salt reading in ppm. Use 0 for a new pool or fresh fill.
- Check the target. It is 3,200 ppm by default, the level Hayward calls optimal for AquaRite; use your own generator’s figure if it differs.
- Add the pounds of salt shown, round to whole bags, then retest after the salt has dissolved and circulated.
How the salt is worked out
First the pool volume. A cubic foot holds 7.48 US gallons, so multiply the pool’s cubic feet by 7.48.
rectangle gallons = length × width × average depth × 7.48
oval or round gallons = 0.785 × length × width × average depth × 7.48
For a round pool, length and width are both the diameter. 0.785 is π ÷ 4, the share of a rectangle that an oval or circle fills.
Then the salt. Parts per million is pounds of salt per million pounds of water, and a gallon of water weighs about 8.34 lb.
pounds of salt = gallons × (target ppm − current ppm) × 8.34 ÷ 1,000,000
Worked example
A 32 × 16 ft rectangular pool, 3.5 ft at the shallow end and 6 ft at the deep end, reading 2,500 ppm, with a 3,200 ppm target.
- Average depth: (3.5 + 6) ÷ 2 = 4.75 ft.
- Volume: 32 × 16 × 4.75 = 2,432 cubic feet, × 7.4805 = 18,193 gallons.
- Salt: 18,193 × (3,200 − 2,500) × 8.34 ÷ 1,000,000 = 106.2 lb.
- Bags: 106.2 ÷ 40 = 2.66, so buy 3 bags of 40 lb pool salt.
Add a bit less than the full amount if you are unsure of the reading. Removing salt means draining water, so it is easier to top up later than to overshoot.
Pool salt chart
Pounds of salt to reach 3,200 ppm, by pool size and current reading. Divide by 40 for the number of 40 lb bags.
| Pool size | From 0 ppm | From 1,500 ppm | From 2,500 ppm |
|---|---|---|---|
| 10,000 gal | 267 lb | 142 lb | 58 lb |
| 15,000 gal | 400 lb | 213 lb | 88 lb |
| 20,000 gal | 534 lb | 284 lb | 117 lb |
| 25,000 gal | 667 lb | 354 lb | 146 lb |
| 30,000 gal | 801 lb | 425 lb | 175 lb |
Adding salt the right way
- Use the right salt. Hayward’s AquaRite manual calls for sodium chloride only, and says not to use rock salt, salt with yellow prussiate of soda, salt with anti-caking additives or iodized salt.
- Run the pump. Turn the circulating pump on, pour the salt into the pool and brush it around. Hayward recommends running the filter pump for 24 hours so the salt spreads evenly, and notes the salt display can take 24 hours to catch up.
- Wait on new plaster. For a new plaster pool, Hayward says to wait 10 to 14 days before adding salt so the plaster can cure.
- Check your own model. Hayward’s AquaRite range is 2,700 to 3,400 ppm with 3,200 optimal. Other generators can use a different range, so check the manual for yours and change the target above.
Common questions
How much salt do I add to my pool?
Multiply your gallons by the ppm you need to add, then by 8.34, and divide by 1,000,000. Raising a 20,000 gallon pool from 2,500 to 3,200 ppm takes 20,000 × 700 × 8.34 ÷ 1,000,000 = 117 lb, or three 40 lb bags.
How many bags of salt for a pool startup?
From 0 ppm to 3,200 ppm you need about 26.7 lb of salt per 1,000 gallons. A 20,000 gallon pool takes 534 lb, which is 14 bags of 40 lb salt (13.3 bags, rounded up).
How much salt for a 25,000 gallon pool?
From fresh water, 667 lb (17 bags of 40 lb) reaches 3,200 ppm. If it already reads 2,500 ppm, it needs 146 lb, or 4 bags.
What salt level should my pool be?
Hayward’s AquaRite manual gives an ideal range of 2,700 to 3,400 ppm, with 3,200 ppm optimal. Other brands can differ, so follow the manual for your salt chlorine generator.
What if my pool has too much salt?
The only way to lower salt is to drain some water and refill with fresh water. To go from 4,000 to 3,200 ppm, replace 20% of the water: 1 − 3,200 ÷ 4,000 = 0.20.
How do I find my pool’s gallons?
Multiply length × width × average depth in feet by 7.48 for a rectangle. For an oval or round pool, multiply by 0.785 first. A 24 ft round pool 4 ft deep holds 0.785 × 24 × 24 × 4 × 7.48 = about 13,500 gallons.
Sources
- Hayward AquaRite owner’s manual. Ideal salt level 2,700 to 3,400 ppm with 3,200 optimal; salt type and how to add salt. Last checked 28 October 2026
- NIST Guide to the SI, Appendix B.9 conversion factors. Cubic foot (0.028 316 85 m³) and US gallon (0.003 785 412 m³), giving 7.48 gallons per cubic foot; pound (0.453 592 4 kg), giving about 8.34 lb for a gallon of water
See the methodology page for how YardageHQ builds and checks its calculators.