Pool Salt Calculator

The Pool Salt Calculator tells you exactly how much salt to add to a saltwater pool to reach the salinity (measured in ppm) that your salt chlorine generator needs. Enter your pool volume, your current salt reading, and a target level — usually around 3,200 ppm — and the tool returns the pounds or kilograms of pool salt to add and the number of bags to buy. If your pool is already over-salted, it instead tells you how much water to drain and refill with fresh water.

How Much Salt Does a Saltwater Pool Need?

A saltwater pool does not sanitize with salt directly. Instead, dissolved salt (sodium chloride) is turned into chlorine by a salt chlorine generator (also called an SWG or salt cell) as water passes through it. For the cell to work, the water has to hold enough salt — typically 2,700 to 3,400 ppm, with about 3,200 ppm as the common ideal. Too little and the cell can't make chlorine; too much and you risk corrosion and scaling.

Pool Salt Formula

Salinity in ppm means milligrams of salt per litre of water, so the amount of salt needed is simply your pool volume multiplied by the change in ppm.

Here \( \Delta\text{ppm} \) is the difference between your target and current salt levels. The factor 8.34 in the imperial version is the weight of one US gallon of water in pounds, which converts volume into the water weight that the ppm ratio acts on.

Worked Example

Suppose you have a 15,000 gallon pool at 0 ppm (freshly filled) and you want 3,200 ppm:

• \( \Delta\text{ppm} = 3{,}200 - 0 = 3{,}200 \)
• Salt = 15,000 × 8.34 × 3,200 ÷ 1,000,000 ≈ 400 lb
• At 40 lb per bag, that is 400 ÷ 40 = 10 bags

Ideal Salt Levels by Generator

Always check your salt cell's manual, but these are the commonly published targets:

Salt to Add by Pool Size (0 → 3,200 ppm)

What Affects How Much Salt You Need

How to Use This Calculator

1. Enter your pool volume: Choose US gallons or metric (litres / m³) and type in the total water volume.
2. Enter current and target salt: Put in your tested ppm (use 0 for a new pool) and the target ppm your generator needs, usually about 3,200.
3. Pick a bag size: Select the salt bag you plan to buy (40 lb, 50 lb, 25 kg or 20 kg).
4. Click Calculate: See the salt to add and the number of bags, or how much water to drain if you're over-salted, plus a visual salinity gauge and step-by-step math.

Frequently Asked Questions

How much salt do I need for my pool?

The amount depends on your pool volume and how far your current salt level is below the target. The formula is salt (lb) = gallons × 8.34 × change in ppm ÷ 1,000,000, or salt (kg) = litres × change in ppm ÷ 1,000,000. For example, raising a 15,000 gallon pool from 0 to 3,200 ppm needs about 400 lb of salt, which is roughly ten 40 lb bags.

What is the ideal salt level for a saltwater pool?

Most salt chlorine generators run best between 2,700 and 3,400 ppm, with about 3,200 ppm being the common ideal. Always check the manual for your specific salt cell, as brands such as Hayward, Pentair and Jandy list slightly different target ranges.

What kind of salt do I add to a saltwater pool?

Use pool-grade salt, which is high-purity (over 99 percent) granular sodium chloride with no additives, anti-caking agents or iodine. Avoid rock salt and table salt. Pool salt dissolves cleanly and will not stain or cloud the water.

How do I lower the salt level if it is too high?

You cannot remove salt chemically, so you dilute it. Drain part of the water and refill with fresh water. To reach the target, drain a fraction equal to 1 − target ÷ current salinity. For example, going from 4,200 to 3,200 ppm means draining about 24 percent of the water. This calculator works that out for you automatically when your current level is above the target.

How long after adding salt can I run the generator?

Add salt with the pump running and brush it around to help it dissolve, then wait about 24 hours and re-test before relying on the salt cell. Running the generator before the salt is fully dissolved and mixed can give a false low reading.

Does adding salt raise my pool water level?

Salt dissolves into the existing water and does not meaningfully change the water level. It also does not evaporate, so once your pool is at the right salinity you usually only add salt to replace losses from splash-out, backwashing, leaks or draining, not from normal evaporation.

Additional Resources

• Parts-per Notation (ppm) - Wikipedia