Water softener size calculator
Hardness & home planning
Change the examples to match your water and system. Results update here in your browser.
Use tested hardness and daily water passing through the softener to calculate a capacity discussion target. The result deliberately separates working capacity at an operating salt dose from an advertised nominal grain rating. It also keeps household peak flow as a separate selection check.
Formulas and planning assumptions
Daily load equals hardness in gpg multiplied by US gallons treated each day. The tool always reports seven-day load and also multiplies daily load by your selected interval. Its working-capacity range runs from that bare interval demand to demand multiplied by 1.20. The upper value includes an editorial 20% load allowance; it is not a manufacturer reserve setting or a certified sizing formula.
Four people at the example 60 gallons per person daily and 10 gpg produce 2,400 grains daily, 16,800 grains over seven days, and a 20,160-grain target with the allowance. The 60-gallon assumption and seven-day interval are editable planning examples. Outdoor water that bypasses treatment does not belong in the load. Learn more about what size softener you need.
Check working capacity and salt together
Capacity-based interval equals entered usable working capacity divided by daily load. Approximate salt use divides 365 days by that interval, then multiplies by your entered pounds per regeneration. These outputs do not simulate calendar overrides; the salt calculator adds that scenario.
Use capacity and salt dose from the same documented operating setting, after any controller reserve. Pentair's 5600SXT system performance sheet illustrates separate capacity-at-dose ratings and rated service flow. Our 24,000-grain and 6-pound defaults are independent examples, not a certified pair or a recommended nominal product size.
Iron and peak flow require another check
The optional dissolved-iron scenario adds 5 gpg per ppm only when you enable it. This is illustrative, not a universal programming instruction or evidence of iron-removal capability. A well-water assessment must distinguish dissolved iron from particles and check the manufacturer's limits.
Finally, compare simultaneous demand with rated service flow and pressure drop. A grain total cannot establish how much water the unit will deliver at an acceptable pressure.