Pool Salt Calculator
Salt (lb) = gallons × 8.34 × ppm to add ÷ 1,000,000. Raising 20,000 gal from 2,400 to 3,200 ppm takes 133.4 lb: 4 bags of 40 lb. Hayward AquaRite aims at 3,200 ppm and Pentair IntelliChlor at 3,400: use the target in your generator's manual.
Salt to add
Test the salt level first and follow your chlorinator’s manual: its target comes first.
133.4 lb
+800 ppm in 20,000 gal
- Bags
- 4 bags of 40 lb
- Raise
- 2,400 → 3,200 ppm (+800 ppm)
- Hayward AquaRite range
- 2,700-3,400 ppm, 3,200 ideal
Worked examples
20,000 gal from 2,400 to 3,200 ppm
- 3,200 − 2,400 = 800 ppm to add
- 20,000 × 8.34 × 800 ÷ 1,000,000 = 133.4 lb
- 133.4 ÷ 40 = 3.3, so 4 bags
Result: 133.4 lb: 4 bags of 40 lb.
Checked by the automated test “pool-salt — 20,000 gal, 2,400 → 3,200 ppm → 133.4 lb, 4 bags of 40 lb”.
Check against Pentair's Table 1
- 20,000 × 8.34 × 3,400 ÷ 1,000,000 = 567.1 lb
- Pentair's table: 568.00 lb, 0.2 % apart
Result: 567.1 lb against 568.00 lb in the table.
Checked by the automated test “pool-salt — Pentair table 1: 20,000 gal, 0 → 3,400 ppm = 568.00 lb within 0.5 %”.
How it works
Salt (lb) = gallons × 8.34 × (target − current ppm) ÷ 1,000,000
Salt (kg) = liters × (target − current ppm) ÷ 1,000,000
Bags = salt ÷ bag size, rounded up
Assumptions
- A gallon of water weighs 8.34 lb and ppm is by weight. The result stays within 0.2 % of Pentair's Table 1 (568.00 lb for 20,000 gal from 0 to 3,400 ppm; 567.1 lb here) and of Hayward's chart (320 lb for 12,000 gal from 0 to 3,200 ppm; 320.3 lb here).
- Targets read in the manuals: Hayward “The ideal salt level is between 2700-3400 ppm … with 3200 ppm being optimal”; Pentair “3000 ppm - 4500 ppm (ideal 3400 ppm)”.
- Bags of 40 lb by default: type the weight printed on your bag.
- At or above the target the calculator gives 0: salt only comes out by draining some water and refilling.
Reference table
| Pool | From 0 ppm | From 1,000 ppm | From 2,400 ppm |
|---|---|---|---|
| 10,000 gal | 267 lb | 183 lb | 67 lb |
| 15,000 gal | 400 lb | 275 lb | 100 lb |
| 20,000 gal | 534 lb | 367 lb | 133 lb |
| 30,000 gal | 801 lb | 550 lb | 200 lb |
Hayward's own chart gives 320 lb for 12,000 gal from 0 ppm; this formula gives 320.3 lb.
Before you buy
- Test first. Measure the salt with a test strip or meter: most pools already hold some. Readings vary by device; Pentair gives its own sensor ±500 ppm.
- Know the volume. Every pound depends on it: use the pool volume calculator if you are not sure.
- Bag weight. Type the weight printed on the bag you buy.
Common mistakes
- Aiming at another brand's figure Hayward's ideal is 3,200 ppm (2,700 to 3,400) and Pentair's 3,400 (3,000 to 4,500): from 2,400 ppm in 20,000 gal, that is 133.4 lb or 166.8 lb.
- Adding salt without testing Pentair: “Most pools contain some salt”, so “the pool owner must always test salt levels before adding salt”. Assuming 0 ppm in a pool already at 2,400 would mean 533.8 lb instead of 133.4 lb.
- Pouring it into the skimmer Pentair spreads the salt around the edge of the pool, “do not add salt through the skimmer”, then brushes and circulates for 24 hours before checking the level again.
- A wrong pool volume Pentair sizes a rectangular pool as length × width × average depth × 7.5: 32 × 16 ft at 5.5 ft is 21,120 gal (21,065 gal with the pool volume calculator's 7.48).
- Going over the maximum Salt does not filter out: Hayward's chart says dilute from 3,600 ppm, above 4,500 ppm Pentair warns of corrosion of pool equipment and surfaces, and the water is drained and refilled 1 ft at a time.
Frequently asked questions
What is the ideal salt level for a pool?
It depends on your salt chlorine generator: Hayward AquaRite 2,700 to 3,400 ppm with 3,200 optimal, Pentair IntelliChlor 3,000 to 4,500 ppm with 3,400 ideal. Below 2,600 ppm the Pentair unit turns off.
How much salt for a pool?
Test the water first, then gallons × 8.34 × ppm to add ÷ 1,000,000: 133.4 lb to raise 20,000 gal from 2,400 to 3,200 ppm, 533.8 lb from 0 ppm only if your test reads 0.
How many bags of salt for a pool?
Divide the pounds by the bag size and round up: 133.4 lb is 4 bags of 40 lb. If your test reads 0 ppm, 20,000 gal takes 14 bags to reach 3,200 ppm.
Sources
Formula, examples and sources checked on by the Yardstick Math team. How we check our formulas.
- AquaRite owner's manual — Hayward, accessed
- IntelliChlor IC15 Salt Chlorine Generator installation and user's guide — Pentair, accessed