Pool Salt Calculator
Salt pounds or kilos to reach target ppm in saltwater pools.
What it does
Saltwater pools still sanitize with chlorine; the cell just manufactures it from dissolved salt. Too little salt starves the cell and throws low salt errors, while too much risks corrosion and salty taste.
The tool above takes pool volume with current and target salt levels in either system. It returns salt to add in pounds or kilos with bag counts.
Test strips read roughly and meters read better, but both beat guessing by pools. Fresh fills, heavy rain, and backwashing all dilute salt after the math was right.
Salt never evaporates, only splashout, leaks, and drains remove it. Levels that keep falling point to water loss worth finding, not to thirsty chemistry.
How to use
- Switch the unit system first: imperial for gallons, metric for cubic meters.
- Enter pool volume from the pool volume calculator.
- Test and enter current ppm.
- Enter the cell manual target, usually near 3200.
Formula
- 8.34
- Pounds per gallon of water.
- ppm gap
- Target minus current salt concentration.
- / 1,000,000
- Parts per million scaling.
Bags round up since salt sells sealed: 40 lb in the US, 20 kg commonly in metric markets. Leftover bags store dry for top ups.
Worked example
Example: 20,000 gal from 500 to 3200 ppm
Pool 20,000 gallons, currently 500 ppm, target 3200.
- Gap: 3200 - 500 = 2,700 ppm.
- Salt: 20,000 x 8.34 x 2700 / 1,000,000 = 450.36 lb.
- Bags: 450.36 / 40 = 11.26, so 12 bags.
- Add with pump running, brush to dissolve, retest tomorrow.
Reference table
| Gap | Pounds | 40 lb bags |
|---|---|---|
| 1,000 ppm | 83.40 lb | 3 |
| 2,000 ppm | 166.80 lb | 5 |
| 2,700 ppm | 225.18 lb | 6 |
| 3,200 ppm | 266.88 lb | 7 |
Limits
- Dilution math only. Cell health needs separate checks.
- Strips read roughly. Meters read better.
- Salt type matters: pool grade dissolves cleanest.
- Leaks drop levels again after dosing.
Common mistakes
- Dosing without testing current level.
- Dumping bags with the pump off, layering brine.
- Targeting the wrong manual number.
- Ignoring falling levels that signal leaks.
- Using rock salt with insoluble impurities.
Try it yourself
Quick checks. Answers sit tucked under each question.
10,000 gal, 0 to 3200 ppm?
10,000 x 8.34 x 0.0032 = 266.88 lb. Then 7 bags of 40 lb.
Metric: 75 m3, 500 to 3200 ppm?
75 x 2700 / 1000 = 202.5 kg. Then 11 bags of 20 kg.
Questions
What ppm do salt pools want?
Usually 2700 to 3400. Check the chlorinator manual for the exact band.
Can I use table salt?
Pool grade salt dissolves cleanest. Additives and caking agents cloud water.
Why does salt keep dropping?
Splashout, backwash, rain overflow, and leaks. Salt never evaporates.
Is saltwater chlorine free?
No. The cell converts salt into chlorine sanitizer continuously.
Does salt damage pools?
High levels corrode metal and stone over time. Hold the manual band.
How soon to retest?
A day after dosing with the pump running, brushed to dissolve.