Water Softener Size Calculator

Work out the grains per week your home needs, and the softener tier to check, from the number of people, your water hardness and any iron.

Grains per week, and the softener tier to check.

People in the home

Hardness (grains per gallon, GPG)

Iron (ppm, optional — leave 0 if unknown)

Iron compensation varies by source (4 or 5 GPG per 1 ppm). This tool uses 4 GPG per 1 ppm as a stated assumption.

Method: people × 75 gallons per day × effective hardness (GPG) × 7 days = grains per week. Confirm the tier with the manufacturer’s sizing guidance.

Disclaimer: All results are estimates for planning only. County and state rules govern — check with your local authority.