Saltwater pools — raise ppm without overshooting the cell
Pool Salt Calculator
Pounds of salt ≈ pool gallons × (target ppm − current ppm) ÷ 120,000. A 15,000 gallon pool raised from 3,200 to 3,400 ppm needs about 25 lb of salt. Enter your volume and readings to get pounds and kilograms.
Salt to add
50.0 lb
- Salt to add
- 22.68 kg
- Salinity increase
- 400 ppm
Worked examples
Top up a mid-size pool
15,000 gallons from 3,200 ppm to 3,400 ppm.
25.0 lb · ≈ 11.34 kg
Fill a new pool with salt
20,000 gallons from 0 ppm to 3,200 ppm.
533.3 lb · ≈ 241.92 kg
Small above-ground pool
8,000 gallons from 2,500 ppm to 3,000 ppm.
15.12 kg · ≈ 33.3 lb
Good for
- Topping up after splash-out and backwashing diluted the water
- First fill of a new salt system before the generator can make chlorine
- Converting a strip reading into a bag count at the pool store
- Checking a contractor’s “add two bags” advice against your gallonage
Common mistakes
- Adding salt when the meter already reads above the manufacturer target
- Using rock salt or water-softener salt with additives the cell forbids
- Retesting before the salt has dissolved and circulated
- Guessing gallons from length × width only and skipping average depth
How to calculate pool salt
- Measure pool volume in US gallons.
- Test current salinity in parts per million (ppm).
- Choose a target ppm from your salt chlorine generator manual.
- Salt (lb) = gallons × (target − current) ÷ 120,000.
- Broadcast salt over the deep end, brush to dissolve, and retest after circulation.
The 120,000 divisor approximates water’s weight and the ppm definition. Always retest; undissolved salt and meter error matter.
Salt needed to raise 1,000 gallons by 100 ppm
Scale linearly: multiply by your gallons ÷ 1,000 and by your ppm increase ÷ 100.
| Volume | Δ ppm | Salt |
|---|---|---|
| 1,000 gal | 100 ppm | 0.83 lb |
| 10,000 gal | 100 ppm | 8.3 lb |
| 15,000 gal | 200 ppm | 25 lb |
Frequently asked questions
What ppm should my saltwater pool be?
Follow the salt chlorine generator manufacturer. Many residential systems target roughly 2,700–3,400 ppm. Too low and the cell underproduces chlorine; too high can damage some equipment.
What kind of salt should I use?
Use pool-grade evaporated salt that is nearly pure sodium chloride, without anti-caking agents or rock salt impurities your manual forbids.
How long until I retest?
After salt dissolves and the pump has circulated—often several hours to overnight—retest and add more only if still low.
My reading is already above target. What now?
Do not add salt. Dilute by replacing some pool water with fresh water, then retest. This calculator will refuse a negative increase.
Sources and updates
Last reviewed .
- Salt dosage approximation – lbs ≈ gallons × Δppm / 120,000 from mass = volume × concentration using ~8.34 lb/gal water.
Planning estimate only. Follow your salt system manual and local pool chemistry guidance. Retest after adding salt.