How much pool salt to add?
Type your pool volume, the salt level your test reads now and the level your chlorine generator wants. The pool salt calculator gives the salt to add in pounds or kilograms and the number of bags, or the share of water to drain when the level is already too high.
- Salt to add
- 338 lb
Add 338 lb of salt to reach 3,200 ppm.
- Bags to buy
- 9
- One bag raises the level by (ppm)
- 319.5
- Water in liters
- 56,781
Salt to add: 338 lb. Add 338 lb of salt to reach 3,200 ppm.
How to calculate
Works out how many pounds or kilograms of salt to add to a saltwater pool to reach a target salt level in ppm, the bags to buy, or how much water to drain when the level is too high.
Example with the default inputs (Pool volume 15,000 gal, Current salt level (ppm) 500, Target salt level (ppm) 3,200, Bag size 40 lb): Add 338 lb of salt to reach 3,200 ppm.
Method: salt (kg) = (target − current) ppm × liters ÷ 1,000,000, with 1 ppm = 1 mg/L; bags = ⌈salt ÷ bag⌉; drain share = 1 − target ÷ current.
- One ppm of salt is one milligram per liter of water, the usual reading of pool test strips and meters.
- Salt dissolves fully and mixes through the whole pool. Water you add or lose later changes the level.
- Draining assumes you refill with fresh water that has no salt.
- Typed numbers are read exactly, so a volume in gallons and a level in ppm give exact amounts, rounded once for display.
Worked examples
Each example is checked against the calculator on every build.
- Pool volume 10,000 gal, Current salt level (ppm) 0, Target salt level (ppm) 3,200, Bag size 40 lb gives Salt to add 267.1 lb, Bags to buy 7, One bag raises the level by (ppm) 479.305709, Water in liters 37,854.11784.Source: U.S. Geological Survey, National Field Manual / IFM conversion factors (1 milligram per liter is about 1 part per million in water), https://pubs.usgs.gov/of/2000/ofr00-213/manual_eng/conversion.html (retrieved 2026-10-02); NIST Special Publication 811, Appendix B (1 US gallon = 3.785411784 L; 1 lb = 0.45359237 kg exactly), https://www.nist.gov/pml/special-publication-811 (retrieved 2026-10-02)
- Pool volume 15,000 gal, Current salt level (ppm) 2,400, Target salt level (ppm) 3,200, Bag size 40 lb gives Salt to add 100.1 lb, Bags to buy 3.Source: U.S. Geological Survey, National Field Manual / IFM conversion factors (1 milligram per liter is about 1 part per million in water), https://pubs.usgs.gov/of/2000/ofr00-213/manual_eng/conversion.html (retrieved 2026-10-02); Hayward Pool Products, How to Lower Salt Levels Within a Swimming Pool (2,700 to 3,400 ppm, best at 3,200 ppm; drain and refill a share of the water), https://www.hayward.com/blog/post/how-to-lower-salt-levels-within-swimming-pool (retrieved 2026-10-02)
- Pool volume 10,000 gal, Current salt level (ppm) 4,000, Target salt level (ppm) 3,500 gives Salt to add 0 lb, Water to drain and refill 12.5%, Volume to drain 1,250 gal.Source: Hayward Pool Products, How to Lower Salt Levels Within a Swimming Pool (2,700 to 3,400 ppm, best at 3,200 ppm; drain and refill a share of the water), https://www.hayward.com/blog/post/how-to-lower-salt-levels-within-swimming-pool (retrieved 2026-10-02): a 10,000 gallon pool at 4,000 ppm, drain about 1/8
- Pool volume 13,209 gal, Current salt level (ppm) 0, Target salt level (ppm) 3,000 gives Salt to add 330.7 lb, Water in liters 50,000.Source: U.S. Geological Survey, National Field Manual / IFM conversion factors (1 milligram per liter is about 1 part per million in water), https://pubs.usgs.gov/of/2000/ofr00-213/manual_eng/conversion.html (retrieved 2026-10-02)
How it works
Pool salt levels are read in parts per million (ppm), which for water is milligrams per liter. With the volume V in liters (1 gallon = 3.785411784 L, 1 m³ = 1,000 L, 1 ft³ = 28.316846592 L):
- salt to add (kg) = (target − current) × V ÷ 1,000,000, when the current level is below the target; otherwise 0
- salt in pounds = kilograms ÷ 0.45359237
- bags to buy = ⌈salt to add ÷ bag size⌉, rounded up to whole bags (0 when no salt is needed)
- one bag raises the level by (bag size in mg) ÷ V ppm
- drain share = 1 − target ÷ current, when the current level is above the target; volume to drain = V × drain share
The volume, levels and bag size are read as the exact decimals you typed, in the unit you typed them, so the amounts are exact and are rounded once for display, halves up.
Rules
- The pool volume is from 1 liter (0.001 m³) to 100,000 m³ (about 26 million gallons). Levels are from 0 to 100,000 ppm, and the target is more than 0. The bag size is from 1 gram to 10,000 kg; leave it empty to skip the bags.
- When the current level equals the target, no salt is added and nothing is drained.
Output format. Salt to one decimal place in pounds (kilograms in Metric); bags as a whole number; ppm per bag to one decimal; drain share as a percent to one decimal; drain volume to the whole gallon (liter in Metric); liters of water to the whole liter.
Worked examples by hand
A new 10,000 gallon pool to 3,200 ppm. V = 10,000 × 3.785411784 = 37,854.11784 L. Salt = 3,200 × 37,854.11784 ÷ 1,000,000 = 121.133 kg = 121.133 ÷ 0.45359237 = 267.05 lb. A 40 lb bag is 18.1436948 kg, so 121.133 ÷ 18.144 = 6.68, 7 bags. One bag raises the level 18,143,694.8 ÷ 37,854.118 = 479.3 ppm.
15,000 gallons from 2,400 to 3,200 ppm. V = 56,781.17676 L; salt = 800 × 56,781.17676 ÷ 1,000,000 = 45.425 kg = 100.14 lb, 2.5 bags, so 3 bags.
10,000 gallons at 4,000 ppm, target 3,500. No salt. Drain 1 − 3,500 ÷ 4,000 = 12.5%, 1,250 gallons (4.732 m³).
50 m³ to 3,000 ppm. V = 50,000 L; salt = 3,000 × 50,000 ÷ 1,000,000 = 150 kg.
Other questions people ask
How much salt do I need for my pool?
Multiply the rise in ppm by the liters of water and divide by 1,000,000 to get kilograms (1 ppm = 1 mg per liter). A new 10,000 gallon pool (37,854 L) at 3,200 ppm needs 3,200 × 37,854 ÷ 1,000,000 = 121.1 kg, about 267 lb or 7 bags of 40 lb.
What salt level should a saltwater pool have?
Use the number in your chlorine generator’s manual. Hayward, for example, gives 2,700 to 3,400 ppm with 3,200 ppm as the best level. Too little salt cuts chlorine output; too much can shut the generator down and makes the water taste salty.
How much does one 40 lb bag raise the salt level?
A 40 lb bag is 18.14 kg, or 18,143,695 mg. In 10,000 gallons (37,854 L) that is 18,143,695 ÷ 37,854 ≈ 479 ppm. In a bigger pool the same bag raises the level less.
How do I lower the salt level?
Salt does not evaporate or wear out, so the only way down is to drain some water and refill with fresh water. Drain the share 1 − target ÷ current: from 4,000 ppm to 3,500 ppm, drain 1 − 3,500 ÷ 4,000 = 12.5%, which is 1,250 gallons of a 10,000 gallon pool.
Why add the salt in steps?
Salt takes time to dissolve and mix, and test strips have some error. Add most of the amount, run the pump for a day, test again, and then add the rest. That way you do not overshoot and have to drain water.