Pool salt calculator
Enter the pool volume, the salt level you measured and the level your chlorinator wants. The calculator gives the salt to add in pounds or kilograms and the number of bags. If the water is already saltier than the target, it shows how much of it to replace with fresh water.
Runs in your browser: nothing you enter is sent anywhere.
How to use
- Choose US or metric units and enter the pool volume.
- Enter the salt reading from your test strip or chlorinator, and the target level.
- Set the bag size and read the salt to add and the bag count.
How it works
ppm (parts per million) is milligrams of salt per kilogram of water, and a litre of water weighs about a kilogram:
- salt (kg) = litres × (target − current) ÷ 1,000,000;
- for US units the gallons are converted to litres (× 3.785) and the result to pounds (÷ 0.4536);
- bags = salt ÷ bag size, rounded up;
- if the current level is above the target: water to replace = 1 − target ÷ current.
Example
A 15,000-gallon pool reads 1,000 ppm and the chlorinator wants 3,200 ppm:
- 15,000 gal × 3.785 = 56,781 L; difference 2,200 ppm;
- 56,781 × 2,200 ÷ 1,000,000 = 124.9 kg = 275.4 lb;
- with 40 lb bags: 275.4 ÷ 40 = 6.9, so 7 bags.
A new 50,000 L pool filled from the tap (0 ppm) and a 3,000 ppm target needs 150 kg: 6 bags of 25 kg.
Tips and common mistakes
- Add a little less than the full amount, let it mix for a day and test again: too much salt is harder to fix than too little.
- Test strips and cell readings can differ by a few hundred ppm; use the same method each time.
- Rain and topping up with fresh water dilute the pool; splash-out and backwashing take salt with the water.
Frequently asked questions
What salt level does a saltwater pool need?
It depends on the chlorine generator. Many cells are designed for roughly 2,700–3,400 ppm, often with 3,200 ppm as the ideal, but some run lower. Use the number in your cell's manual or on its display.
How much salt to raise a pool by 1,000 ppm?
1,000 ppm is one part in a thousand by weight. For 10,000 gallons (about 37,850 L of water, 37,850 kg) that is 37.85 kg, or about 83 lb. Double the volume, double the salt.
Can I lower the salt level?
Only by dilution: salt does not evaporate or filter out. Draining part of the water and refilling with fresh water lowers it in proportion. To go from 4,000 to 3,200 ppm you replace 20 % of the water.
What kind of salt should I use?
Pool salt sold for chlorinators: high-purity sodium chloride without anti-caking agents or iodine. Pour it in, brush it around and run the pump; the reading settles after the salt dissolves and mixes.