Water Softener Calculator

What size water softener do I need?

people
gal
grains per gal
grains

Your home removes about

21,000grains per week

People × gallons × hardness per day, the extension method. Iron is not included, so treat iron separately using the softener maker's guidance.

One week of hardness against softener capacity32,000 grainsGrains per week: 21,000Left in the unit: 11,000
Grains per day3,000
Days between regenerations10.7
32,000 grain unit10.7 days

Find how many grains of hardness your household removes each week and how long a unit will last between regenerations.

How it works

People times gallons per day times grains of hardness gives daily grains. Divide softener capacity by that to see days between cycles.

Before you order

  • Get hardness from a recent test or your water supplier in grains per gallon.
  • A longer cycle uses salt more efficiently at the unit's lower salt settings.
  • Iron can foul the resin, so test for it before choosing a unit.

Common questions

How do I convert ppm to grains?

Divide ppm of hardness by 17.1 to get grains per gallon.

Should I include iron?

Add it only using your softener maker's method, since published allowances vary.