Pool Salt Calculator
Find how much salt to add to a saltwater pool to reach the salt level your chlorinator needs, and how many bags to buy. Enter your pool's volume, or its size and water depth, and the salt level you measured.
- Choose US or Metric. This also sets the units of the results and the bag sizes: 40 lb bags for US, and 25 and 20 kg bags for Metric.
- Under Pool volume, choose Enter volume and enter the volume from your pool's specs or your chlorinator's settings, in gallons, liters, or cubic meters. If you don't know it, choose Calculate from dimensions and enter the shape, size, and water depth of the pool.
- For a pool with a sloped bottom, keep Shallow and deep ends and enter the water depth at each end. Use Add section for a deep end that drops off sharply or a sun shelf, and set a section to Subtract for steps or a bench.
- Enter the Current salt level from a test strip, a test kit, or your chlorinator's display. Enter 0 only for fresh fill water. If your chlorinator shows salt in g/L, such as 3.2, choose g/L as the unit.
- The Target salt level starts at 3,200 ppm. Enter the level in your chlorinator's manual. The reset link under the field brings back 3,200 ppm.
- If your bag is not listed, enter the weight printed on the bag in Custom bag size to add it to the results.
- Optionally, enter a price per bag, pound, or kilogram to estimate the cost.
The volume and salt level fields accept whole numbers and decimals, such
as 15,000 or 3.2. The dimension and depth fields
also accept fractions and mixed numbers, such as 3 1/2.
How much salt to add
Salt levels are measured in parts per million (ppm). One ppm is one milligram of salt in a liter of water, and 1 g/L is 1,000 ppm. The salt you need is the increase in salt level times the volume of water:
Salt increase = target salt level − current salt level
Kilograms of salt = salt increase (ppm) × liters ÷ 1,000,000
Pounds of salt = salt increase (ppm) × gallons × 8.345 ÷ 1,000,000
The calculator treats pool salt as pure sodium chloride that dissolves evenly in all the water, and it adds no extra. The same formula gives the amounts in the salt charts from chlorinator makers: Pentair's IntelliChlor guide lists 300.43 lb to bring 10,000 gallons from 0 to 3,600 ppm, and Jandy's AquaPure manual lists 113 kg (250 lb) to bring 10,000 gallons from 0 to 3.0 g/L. Morton says each 40 lb bag adds 480 ppm to 10,000 gallons; the formula gives about 479 ppm.
The number of bags is:
Bags = pounds (or kilograms) of salt ÷ weight per bag, rounded up
The calculator shows these bag sizes:
| Bag | Sold as |
|---|---|
| 40 lb | Morton Professionals' Choice and Diamond Crystal Splash Ready (US) |
| 25 kg | Bosta Poolsel (UK) |
| 20 kg | Sable Marco and Windsor (Canada), Sunray (Australia), and Dominion Salt (New Zealand) |
Target salt level
Each chlorinator works within its own salt range, so use the level in your manual. Some examples from maker manuals:
| Chlorinator | Salt level |
|---|---|
| Hayward AquaRite | 2,700 to 3,400 ppm, with 3,200 ppm as optimal |
| Pentair IntelliChlor | 3,600 to 4,500 ppm, with 3,600 ppm as ideal |
| Jandy AquaPure | 3.0 to 3.5 g/L (3,000 to 3,500 ppm) |
| Zodiac EL Series (Australia) | 4,000 ppm |
The calculator starts at 3,200 ppm, a level inside the Hayward and Jandy ranges and inside the range Pentair shows as good salt. Many chlorinators sold in Australia run at about 4,000 ppm. Hayward notes that salt starts to taste at about 3,500 to 4,000 ppm.
Pool volume
With Calculate from dimensions, the volume is the area of each section times its average water depth:
Average depth = (shallow end depth + deep end depth) ÷ 2
| Shape | Area |
|---|---|
| Rectangle | length × width |
| Circle | π × diameter² ÷ 4 (or π × radius²) |
| Oval | π × length × width ÷ 4 |
| Kidney | (width A + width B) × length × 0.45 |
| Known area | the area you enter |
Measure the depth from the bottom to the water surface, not to the top of the wall. Width A and Width B of a kidney pool are the widest points across each of its two lobes, and the kidney formula is an estimate. For an oval above-ground pool with straight sides, enter a rectangle (the length minus the width, by the width) and a circle (the width across).
Many pool guides multiply cubic feet by 7.5 gallons. The calculator uses the exact 7.48 gallons per cubic foot, so its volume is about 0.26% less.
If your salt level is too high
No chemical removes salt from pool water. When the salt level is above the target, the calculator shows 0 lb. To lower it, drain part of the water and refill with fresh water. Replacing about a tenth of the water lowers the salt level by about a tenth. If the fill water has no salt, the share to drain is:
Share to drain = 1 − target salt level ÷ current salt level
For example, going from 3,800 ppm to 3,200 ppm means replacing about 16% of the water. Drain and refill in steps and test between them, since tap water can contain some salt.
Examples
A 20,000 gallon pool with fresh water
To bring 20,000 gallons of fresh water from 0 to 3,200 ppm, add 534 lb (242 kg) of salt: 14 bags of 40 lb. At $8 per bag, the cost is $112.00.
Topping up a pool
If the same pool tests at 2,700 ppm, raising it to 3,200 ppm takes 83 lb (38 kg) of salt: 3 bags of 40 lb.
A pool measured from its dimensions
A rectangular pool 32 ft by 16 ft, 3 1/2 ft deep at the shallow end and 6 ft deep at the deep end, has an average depth of 4.75 ft and holds about 18,193 gallons. Bringing fresh water to 3,200 ppm takes 486 lb of salt: 13 bags of 40 lb.
Metric
A 50,000 liter pool at 2.2 g/L needs 1 g/L more to reach 3.2 g/L. That's 50 kg of salt: 2 bags of 25 kg or 3 bags of 20 kg.
FAQ
About 534 lb, or 14 bags of 40 lb, to bring fresh water from 0 to 3,200 ppm. If the water already tests at 2,700 ppm, it takes about 83 lb, or 3 bags.
About 7 bags of 40 lb (267 lb) to bring fresh water from 0 to 3,200 ppm. Each 40 lb bag raises 10,000 gallons by about 479 ppm.
It depends on the chlorinator, usually somewhere from 2,700 to 4,500 ppm. Hayward gives 3,200 ppm as optimal, Pentair recommends 3,600 ppm, and Jandy recommends 3,000 to 3,500 ppm. Check the manual for yours.
Yes. One g/L is 1,000 ppm, so a chlorinator that shows 3.2 g/L is reading 3,200 ppm. Choose g/L as the unit to enter the reading as it is shown.
Drain part of the water and refill with fresh water. Replacing about a tenth of the water lowers the salt level by about a tenth. No chemical removes salt.
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