Water Softener Size Calculator
Work out the usable grain capacity your household needs, using a measured hardness reading.
How the calculation works
Daily grains = people × gallons per person × hardness in GPG. Required usable capacity = daily grains × (days between regenerations + one reserve day).
For four people using 60 gallons each at 15 GPG over seven days, the daily load is 3,600 grains. Seven days plus a one-day reserve require 28,800 grains of usable capacity.
Why an advertised 32,000-grain model may not be enough
Capacity varies with the salt dose used to regenerate the resin. Ask for the manufacturer's capacity at the efficient salt setting you intend to use. Also compare service flow, pressure loss, available drain and electrical connections, and any iron or manganese treatment requirements.
This tool estimates hardness load. It does not select a particular model, prescribe an iron adjustment, or replace the equipment manual.
Montana State University: household water softener guidanceNeed a hardness reading?
Look up local water data for context, then test your untreated tap water. A city range or state estimate is not a softener setting for your home.
Compare buying options
These manufacturer links are starting points for comparison. We have not installed or independently tested these systems. Check the required capacity and flow before choosing a model.
SpringWell
Salt Water Softener System
Homeowners comparing a directly purchased softener with a separate installation quote
Useful for: Ion-exchange softening; Multiple system options to compare.
Limitations: Needs salt and a suitable drain; Confirm usable capacity, service flow and installation costs.
Whirlpool
Water Softener Selection Tool
Homeowners comparing manufacturer options after measuring hardness
Useful for: Household and hardness-based selection; Links to manufacturer product options.
Limitations: Manufacturer selection covers its own range; Confirm plumbing and drain requirements.