What Size Water Softener Do I Need? Sizing Calculator
How to calculate the right water softener grain capacity for your household.
The sizing formula
Daily softening requirement = (number of people) x (gallons per person per day) x (hardness in GPG). The standard estimate is 75 gallons per person per day. For a family of 4 with 15 GPG water: 4 x 75 x 15 = 4,500 grains per day. Multiply by 7 for weekly capacity: 31,500 grains. A 32,000-grain softener would regenerate roughly once per week.
Common sizes
24,000 grain: 1-2 people, moderate hardness. 32,000 grain: 2-3 people, hard water. 48,000 grain: 3-5 people, hard to very hard water. 64,000 grain: 5+ people or extremely hard water. When in between sizes, go up. Oversizing slightly is better than undersizing.
Check your water first
You need to know your hardness in GPG before sizing. Iron content also factors in: add 5 GPG for every 1 PPM of iron detected. See our product comparisons for systems in each size range.