Home Cleaning Calculators
Water softener salt usage.
Work out how often your softener regenerates and how much salt that uses in a year. Enter your water hardness, household water use and the capacity and salt dose from your softener's spec sheet. Runs in your browser; nothing is sent or stored.
Your numbers
Result
Fill the form and press Calculate.
Worked example
Water at 10 grains per gallon and a household of 4 using 75 US gallons each a day (300 gallons) means 10 x 300 = 3,000 grains of hardness to remove daily. A softener rated for 20,000 grains per regeneration at 6 lb of salt lasts 20,000 / 3,000 = 6.67 days, rounded down to 6 days. That is 60.8 regenerations and 365 lb of salt a year; with 40 lb bags at $7 that is 9.1 bags, $63.88. Keep a 25% reserve and it regenerates every 5 days instead. These are example inputs: replace them with your own.
How it works
Grains used per day = hardness (gpg) x gallons of water per day. Days between regenerations = capacity x (1 - reserve) / grains per day, rounded down. Salt per year = 365 / days x salt per regeneration. The Water Quality Association's glossary describes rated softening capacity as what the manufacturer states the unit removes between regenerations at a stated salt dose, so capacity and salt dose must be taken as a pair from the spec sheet.
Conversions. One grain per gallon equals 17.1 mg/L (ppm) as calcium carbonate, per the Water Quality Association. 1 US gallon = 3.785 litres.
Not covered. Dissolved iron and manganese are not included; neither are timer-based units that regenerate on a fixed schedule regardless of use, or salt-free conditioners (which do not remove hardness; see the WQA page on scale deposits). Real units vary, so treat the result as an estimate.
Sources and basis (pages opened 2026-10-08): Water Quality Association, Glossary of Terms; Water Quality Association, Scale Deposits.
FAQ
How often does a water softener regenerate?
Capacity (after any reserve) divided by the hardness you use per day. Harder water and more people mean more frequent regeneration.
How much salt does a water softener use?
Salt per regeneration, from the spec sheet, times the number of regenerations a year. The calculator does that sum with your figures.
How do I convert mg/L to grains per gallon?
Divide by 17.1. One grain per gallon equals 17.1 mg/L as calcium carbonate, per the Water Quality Association glossary.
What is reserve capacity?
Some softeners hold back part of their capacity so they regenerate before running out. Enter the share as a percentage, or 0 if yours does not.
Does this work for timer-based softeners?
No. A timer-based unit regenerates on a fixed schedule; use its schedule and salt dose directly.