What Size Water Softener Do You Need?
Enter your hardness and household size. We run the same grain-load math water-treatment pros use, including iron compensation, and give you a capacity, a regeneration cadence, and the yearly salt bill, not just a model name.
How the math works
Daily grain load: people × gallons per person per day (about 75) × hardness in grains per gallon (GPG). A family of four on 10 GPG water produces 4 × 75 × 10 = 3,000 grains per day. Iron compensation: each 1 ppm of dissolved iron works the resin like roughly 4 GPG of extra hardness, so well water gets sized harder than its test strip suggests. Capacity: pick the standard size (24k–80k) that handles about a week of load while keeping 25% in reserve, regenerating every 7–10 days is the efficiency sweet spot. Our sizing guide walks each step with examples.
If your hardness tests under 3.5 GPG you may not need a softener at all, see the hard water guide. On well water with visible iron staining, read the well-water softener rules before buying anything.
Or browse by sizing question
- The sizing guide (grain math)
- How to test your hardness
- Best water softeners
- High-efficiency systems
- What softeners really cost
- Softeners for well water
- Salt types & usage
- All softener types