';stepsHTML+='1. Target ('+tar+' ppm) – Current ('+cur+' ppm) = '+diff+' ppm increase needed.
';stepsHTML+='2. Formula: (Volume × '+constant+' × Change in PPM)
';stepsHTML+='3. Calculation: ('+vol+' × '+constant+' × '+diff+') = '+saltNeeded.toFixed(2)+' '+weightLabel+' of salt.
';stepsHTML+='Required Bags (Approximate):
';if(unit==='imperial'){stepsHTML+='- '+(saltNeeded/40).toFixed(1)+' bags (40 lb bags)
';}else{stepsHTML+='- '+(saltNeeded/20).toFixed(1)+' bags (20 kg bags)
';}document.getElementById('stepDetails').innerHTML=stepsHTML;document.getElementById('stepDetails').style.display=showSteps?'block':'none';}
How to Use the Pool Salt Calculator
Maintaining a saltwater swimming pool requires precision to ensure your salt chlorine generator (SCG) operates efficiently. This pool salt calculator helps you determine the exact weight of salt needed to reach your target salinity level, usually expressed in parts per million (ppm).
To get an accurate result, you will need to know your pool's total water capacity and your current salt concentration. Most salt cells require a range between 2,700 and 3,400 ppm, with 3,200 ppm being the industry standard "sweet spot."
- Measurement System
- Choose between Imperial (US) units using gallons and pounds, or Metric units using liters and kilograms.
- Pool Volume
- The total amount of water your pool holds. If you are unsure, common rectangular pools (32×16) usually hold approximately 15,000 to 18,000 gallons.
- Current Salt Level
- The current reading from your digital salt tester or test strips. Never trust the salt cell's display alone, as these can be inaccurate if the cell is dirty.
- Target Salt Level
- The desired ppm level recommended by your salt chlorinator manufacturer.
The Pool Salt Formula
When calculating salt additions, we use the weight of water as the baseline. Because 1 gallon of water weighs approximately 8.34 pounds, we use this constant to convert parts per million into physical weight.
Pounds of Salt = (Pool Volume × 0.00000834) × (Target PPM – Current PPM)
- Volume: Total gallons of water in the pool.
- 0.00000834: The conversion factor (8.34 lbs per gallon / 1,000,000).
- PPM Difference: The gap between where you are and where you want to be.
Step-by-Step Calculation Example
Example Scenario: You have a 20,000-gallon pool. Your test strip shows a current salt level of 2,500 ppm, but your salt generator manual recommends a target of 3,200 ppm.
Solution:
- Determine the PPM Increase: 3,200 – 2,500 = 700 ppm.
- Multiply Volume by the Constant: 20,000 × 0.00000834 = 0.1668.
- Calculate Total Weight: 0.1668 × 700 = 116.76 lbs.
- Result: You need approximately 117 lbs of salt, which is roughly three 40lb bags.
Common Questions
What kind of salt should I use?
You should only use high-purity (99% or higher) sodium chloride (NaCl) specifically labeled as "Pool Salt." Avoid rock salt, water softener salt with additives, or iodized table salt, as these contain impurities that can stain your pool finish or damage the electrolytic cell.
How do I add the salt to the pool?
Turn on your pool pump to ensure circulation. Pour the salt around the perimeter of the deep end of the pool. Use a pool brush to spread the salt and help it dissolve faster. Do not let salt sit in a pile on the bottom, especially in vinyl liner or fiberglass pools, as it can cause damage or staining. Keep the pump running for at least 24 hours to ensure the salt is fully integrated before turning on the salt chlorine generator.
Why is my salt level dropping?
Salt does not evaporate. If your salt levels are dropping, it is usually due to "water loss" where water is physically leaving the pool. This includes splash-out, backwashing the filter, or a leak. When you top off the pool with fresh water, the salt concentration is diluted, requiring the use of a pool salt calculator to determine the refill amount.