Well Water Softener Size Calculator
Softener capacity is sized from the hardness your household removes each day. We multiply people × gallons per person × hardness in grains per gallon, the same method Penn State Extension and Angi use. If your water has dissolved iron, we add 4 extra gpg for each ppm of iron.
Enter your hardness (from a lab report or test strip) and household size to get a recommended softener capacity. If you have lab results, enter them to check against EPA standards — some issues need treatment other than a softener.
Related guides
How this works
Softener capacity is sized from the hardness your household removes each day. We multiply people × gallons per person per day × hardness in grains per gallon, the same method Penn State Extension and Angi use. Then we multiply by the number of days you want between regenerations. If your water has dissolved iron, we add 4 gpg of 'compensated hardness' for each ppm of iron, following SoftPro's published formula, because iron uses up resin capacity. We then match the result to the smallest standard residential size (24,000–96,000 grains) and show Angi's published 2026 unit price range for that size, with installation labor listed separately.
The optional lab check compares each number you enter with the U.S. EPA's drinking-water standards. These are primary (health-based) maximum contaminant levels and secondary (cosmetic and aesthetic) standards, as published on epa.gov. We do not make health judgments. We show where a result sits relative to EPA's number, which kind of treatment is usually priced for it, and when to talk to your local health department. Cost ranges come from Angi and HomeGuide. Published by Cornelia Cove LLC.
Estimates only — independent local providers quote their own pricing. Data last reviewed 2026-10.
Sources
- Penn State Extension — Water Softening (Sep 2025)
- HomeGuide — Water Softener Cost (third-party estimate)
- SoftPro — Hardness compensation formula
- EPA — National Primary Drinking Water Regulations
- EPA — Secondary Drinking Water Standards
Frequently Asked Questions
What size water softener do I need for well water?
Multiply people × daily gallons × hardness (gpg), then × days between regenerations. A family of four using 90 gallons each at 10 gpg needs 25,200 grains for a 7-day cycle (Angi's example). That rounds up to a 32,000-grain unit.
Does iron change the size?
Yes. Each ppm of iron is commonly counted as about 4 extra grains of hardness (SoftPro). Above about 1–2 ppm, a separate iron filter is usually recommended ahead of the softener (HomeGuide).
My report says hardness in mg/L. How do I convert?
Divide by 17.1 to get grains per gallon. Penn State rounds the factor to 17.
Will a softener fix nitrate, arsenic, or bacteria?
No. Those need different treatment and a health-department conversation. The tool flags them so you can get the right quote.
Rather skip straight to quotes?
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