How the Pool Salt Calculator Works
Saltwater pools use a salt chlorine generator (also called a salt cell or SWG) to convert dissolved salt into chlorine through electrolysis. That only works within a specific salinity window, so owners periodically test the water in parts per million (ppm) and top up with pool-grade salt (sodium chloride) when the reading drifts below the cell's target range. This calculator applies the standard pool-industry formula to tell you exactly how much salt to add.
The formula
The amount of salt needed follows directly from the weight of water in the pool and the size of the gap between your current and target readings:
- Pounds of salt = pool gallons × 8.34 × (target ppm − current ppm) ÷ 1,000,000
The constant 8.34 is the weight in pounds of one US gallon of fresh water. Multiplying by pool volume converts gallons into total pounds of water, and ppm (parts per million) is simply pounds of salt per million pounds of water. So the formula scales the ppm gap you need to close by the total weight of water that gap has to be dissolved into.
Typical salt ranges
Most residential salt chlorine generators are designed to operate between 2,700 and 3,400 ppm, with many manufacturers centering their recommendation around 3,200 ppm. Below roughly 2,700 ppm, many cells throttle output or display a low-salt error; above roughly 4,500-6,000 ppm, water can taste salty, corrode metal fixtures faster, and eventually damage the cell. Always confirm the exact range in your salt cell's manual, since it varies by brand and model.
Tips for adding pool salt
- Turn off the salt cell (but keep the pump circulating) while you add salt, and only turn the cell back on once it has fully dissolved.
- Broadcast salt evenly around the pool's perimeter in the deep end rather than pouring it in one pile, which slows dissolving and can bleach vinyl liners.
- Brush any salt that settles on the floor or steps to help it dissolve faster.
- Wait at least 24 hours of circulation before retesting - undissolved salt will not register on a test strip, kit, or the cell's digital reading.
- If your reading is already at or above your target, do not add salt; the only way to lower salinity is to partially drain and refill with fresh water.