Water Softener Size Calculator
Find the right grain capacity.
Special
Water Softener Regeneration Calculator
See how many days your softener can run between regenerations for your hardness and household, and roughly how much salt and water those regenerations use each year.
How it works
- Enter the softener’s grain rating from its label or manual and choose the salt setting it is programmed for.
- Choose how the valve keeps reserve capacity: metered valves typically hold back about a day of use.
- Enter water hardness (and iron, if known) and your household size.
- Read the regeneration interval, the number of regenerations per year and the estimated salt use.
Formula
Daily load = people × gallons per person × (hardness + 4 × iron) Usable capacity = rating × salt-setting factor (100% / 80% / 67%) Days between regenerations = ⌊(usable capacity − reserve) ÷ daily load⌋ Salt per regeneration = usable capacity ÷ grains removed per lb of salt
Standard resin removes about 2,000 grains per pound of salt at the high (≈15 lb/ft³) setting, 2,667 at the medium (≈9 lb/ft³) setting and 3,333 at the efficient (≈6 lb/ft³) setting. Regeneration water is estimated at about 50 gallons per cubic foot of resin, with 32,000 grains of rating per cubic foot.
Example
A two-person household with 20 gpg water and a 32,000-grain softener on the efficient salt setting, with a metered valve.
Inputs
- Softener rating
- 32,000 grains
- Salt setting
- Efficient (≈6 lb/ft³)
- Reserve
- One day of use (metered)
- Water hardness
- 20
- Hardness unit
- gpg
- Iron (optional)
- 0 ppm
- People in the home
- 2
- Use per person
- 70 gal/day
Result
Regenerates about every6 days6.7 days of soft water after the reserve
Regenerations per year≈ 61
Salt per year≈ 391 lb
40-lb bags per year≈ 10
Metered vs. timer regeneration
A metered (demand-initiated) valve counts gallons and regenerates when the remaining capacity drops below its reserve, so the interval follows your actual use. A timer valve regenerates on fixed days whether or not the resin is exhausted; set it a day or two shorter than the “no reserve” result so hardness never breaks through.
If the interval is only a few days, the softener is working hard: a larger rating or a higher salt setting lengthens it. If it is several weeks, a calendar override keeps the resin bed fresh.
Frequently asked questions
How often should a water softener regenerate?
Most residential softeners are sized to regenerate every 3–10 days. More often than every two or three days suggests the unit is undersized; less often than every two weeks is usually limited by a calendar override.
How much salt does a water softener use per year?
It depends on hardness, water use and the salt setting. A family of four with 12 gpg water on a medium setting typically uses roughly 500–600 lb a year, because each regeneration also refreshes the unused reserve. Enter your own figures above.
Does a lower salt setting save money?
Yes, per grain removed. The efficient setting removes about two-thirds more hardness per pound of salt than the maximum setting, at the cost of more frequent regenerations.
What is reserve capacity?
Capacity held back so the resin does not run out before the next scheduled regeneration, usually overnight. Metered valves typically estimate one day of water use as the reserve.