Pool Salt Calculator

Quick Answer

Last updated: 10 November 2026 ·How we calculate this: parts-per-million by weight with 8.34 lb per gallon of water

How This Pool Salt Calculator Works

A saltwater pool uses a salt chlorine generator (salt cell) to make chlorine from dissolved salt. The cell only works well when the salt level is in the range its maker sets, often around 3,000 to 3,200 parts per million (ppm). Enter your pool's volume in gallons, the salt level from your test strip or meter, and the target level. The calculator gives the pounds of salt and the number of bags to add, or, if the salt is already too high, how much water to drain and replace.

How to Use the Pool Salt Calculator

1. Enter your pool volume in US gallons.
2. Test the water and enter the current salt level in ppm.
3. Enter the target salt level from your generator's manual.
4. Enter your bag size, usually 40 lb.
5. Press Calculate, add the salt in stages and retest after 24 hours.

Pool Salt Formula

• Weight of water: gallons × 8.34 lb
• Salt to add (lb): gallons × 8.34 × (target − current) ÷ 1,000,000
• Bags: pounds ÷ bag size, rounded up
• Share of water to replace if salt is high: 1 − target ÷ current
• Units: 1 ppm = 1 lb of salt per million lb of water; 1 US gallon = 3.785 liters

Key Terms

• ppm: parts per million; for pool salt, pounds of salt per million pounds of water.
• Salt chlorine generator: equipment that turns dissolved salt into chlorine by electrolysis.
• Salt cell: the part of the generator where electrolysis happens.
• Pool-grade salt: sodium chloride of at least 99% purity without additives.
• Backwashing: reversing water through a filter to clean it, which removes some pool water.

Worked Example

A 20,000-gallon pool tests at 2,400 ppm and the generator needs 3,200 ppm.

• Increase needed = 3,200 − 2,400 = 800 ppm
• Salt = 20,000 × 8.34 × 800 ÷ 1,000,000 = 133.4 lb
• That is 4 bags of 40 lb (buy 4 and keep any extra for later)

Real-Life Examples

• New saltwater pool: 15,000 gallons needs 400 lb (11 bags) to reach 3,200 ppm.
• Spring top-up: 20,000 gallons at 2,400 ppm needs 133 lb.
• Small top-up: 10,000 gallons from 3,000 to 3,400 ppm needs 33.4 lb.
• Over-salted pool: find how much water to drain and refill.

Saltwater Pool vs Traditional Chlorine Pool

• Saltwater pool: a salt cell makes chlorine from salt; softer-feeling water and fewer chlorine purchases, but a cell to replace every few years.
• Traditional chlorine pool: chlorine is added as tablets, liquid or granules; lower equipment cost but more handling of chemicals.
• Both are chlorine pools and need the same pH and chlorine testing.

Pounds of Salt by Pool Size

At 8.34 lb per gallon of water.

Tips for Adding Pool Salt

Know your pool's real volume: it is the biggest source of error. Use the Pool Volume Calculator if you are not sure. Test with a fresh salt test strip or a digital meter, and compare with the reading on your generator's control panel, which can drift. Add salt with the pump running, pour it around the shallow end, brush it so it does not sit on the floor, and wait at least 24 hours before retesting. Adding salt in two or three steps avoids overshooting.

Salt does not evaporate, so you only need to replace what leaves with water: splash-out, backwashing, draining and rain overflow. Too little salt makes the cell produce less chlorine and can shorten its life; too much can corrode metal parts and make the water taste salty. Use plain pool salt without iodine or anti-caking agents.

Common Mistakes to Avoid

• Guessing the pool volume. A 20% volume error means a 20% salt error.
• Adding all the salt at once. Add in stages and retest after it dissolves.
• Trusting an old test strip. Use fresh strips or a meter.
• Using rock salt or iodized salt. Use pure pool-grade salt.
• Adding salt to fix low chlorine. Check the cell and stabilizer before adding more salt.

Frequently Asked Questions

References & Sources