Water Softener Salt Calculator

A family of 4 with 15 gpg water and a 48,000-grain softener set to 9 lb of salt per cubic foot uses about 590 lb of salt a year, close to 50 lb a month. That's 15 bags of 40 lb, or about $105 a year at $7 a bag. A timer valve set to every 7 days uses about 700 lb.

People in your home

Iron (ppm, from your water test)

Water use per person per day

60 gal75 gal80 gal

Iron allowance

4 gpg per ppm5 gpg per ppm

Water hardness

Softener size

Not sure? Use the size calculator.

Salt setting

Valve type

Metered (regenerates when needed)Timer (fixed schedule)

Bag size

40 lb50 lb

Price per bag ($)

591 lb of salt a year

About: 49.3 lb a month
Bags of 40 lb a year: 15
About: $105 a year
Regenerations a year: 43.8, every 8.3 days
Salt per regeneration: 13.5 lb

Show the math

salt per regeneration = 1.5 × 9 = 13.5 lb

regenerations per year = 365 × 4,500 ÷ 37,500 = 43.8

salt per year = 43.8 × 13.5 = 591 lb

bags = ceil(591 ÷ 40) = 15

Salt a year for this home at each setting (metered)

6 lb

493 lb

9 lb

591 lb

12 lb

717 lb

15 lb

821 lb

591 lb of salt a yearBack to calculator

How to use this calculator

Enter your household and water hardness. Add iron if a test showed any.
Pick your softener's size. It's on the tank label or in the manual, often as grains (for example 32,000) or cubic feet of resin.
Pick the salt setting from your control valve. If you don't know, leave 9 lb.
Choose metered if your valve counts gallons, or timer if it regenerates on set days.
Enter your bag size and what you pay per bag to see the yearly cost.

The formula

Your softener uses salt every time it regenerates, so yearly salt is regenerations per year times salt per regeneration.

Salt per regeneration = cubic feet of resin × salt setting (lb per cubic foot)

Regenerations per year (metered valve) = 365 × grains per day ÷ softener capacity at that salt setting

A timer valve regenerates on its schedule no matter how much water you used, so it's simply 365 ÷ the days between regenerations.

Example 1: family of 4, 15 gpg, 48,000-grain softener, 9 lb setting, metered. The home uses 4,500 grains a day. At 9 lb the 1.5 cubic feet of resin holds 37,500 grains, so the softener regenerates about every 8.3 days, or 43.8 times a year. Each regeneration uses 1.5 × 9 = 13.5 lb of salt. That's 591 lb a year, or 15 bags of 40 lb. On a timer set to every 7 days the same softener regenerates 52 times and uses about 704 lb.

Example 2: couple, 10 gpg, 1 ppm iron, 24,000-grain softener, 6 lb setting, metered. Hardness with iron is 14 gpg, so the home uses 2,100 grains a day. At 6 lb, 0.75 cubic feet of resin holds 15,000 grains, about 7.1 days of water. That's 51.1 regenerations a year at 4.5 lb each, or 230 lb of salt: 6 bags.

What this calculator doesn't cover

Your valve's reserve setting. Metered valves keep some capacity in reserve, so real use can be a little higher than shown.
Potassium chloride. It takes about 13 to 15% more by weight to do the same job as sodium chloride.
Salt bridges or mushing in the brine tank. If the level never drops, check for a bridge before adding more salt.
Water used for regeneration (backwash and rinse), which this page doesn't count.
Iron above 2 ppm or other problems that shorten resin capacity.

Yearly salt by household and hardness (48,000-grain softener, 9 lb setting, metered, 75 gal per person)

People	5 gpg	10 gpg	15 gpg	20 gpg	25 gpg
2	99 (3)	197 (5)	296 (8)	394 (10)	493 (13)
3	148 (4)	296 (8)	443 (12)	591 (15)	739 (19)
4	197 (5)	394 (10)	591 (15)	788 (20)	986 (25)
5	246 (7)	493 (13)	739 (19)	986 (25)	1,232 (31)

Each cell is pounds of salt per year, with 40 lb bags in brackets.

Salt per regeneration by size and setting (lb)

Size	6 lb	9 lb	12 lb	15 lb
24,000 (0.75 cu ft)	4.5	6.8	9.0	11.3
32,000 (1.0)	6.0	9.0	12.0	15.0
48,000 (1.5)	9.0	13.5	18.0	22.5
64,000 (2.0)	12.0	18.0	24.0	30.0
80,000 (2.5)	15.0	22.5	30.0	37.5
96,000 (3.0)	18.0	27.0	36.0	45.0

(6.75 shows as 6.8 and 11.25 as 11.3: round half up to 1 decimal.)

Tips

Lower salt settings get more softening per pound. At 6 lb per cubic foot resin softens about 3,333 grains per pound of salt; at 15 lb it's about 2,000.
NSF/ANSI 44 counts a softener as efficient at 3,350 grains or more per pound of salt, and it must use a metered valve.
Keep the brine tank at least a quarter full and the salt level a few inches above the water.
Use pellets or crystals made for softeners. Rock salt leaves more insoluble residue in the tank.
If your salt use suddenly drops to zero, look for a hard crust (a salt bridge) and break it up gently with a broom handle.

(Tips 3 to 5 are general practice; keep them exactly as written, no extra claims.)

FAQ

How much salt does a water softener use per month?

Most homes use roughly 20 to 80 lb a month. A family of 4 with 15 gpg water on a 48,000-grain metered softener at 9 lb per cubic foot uses about 49 lb a month. A couple with 10 gpg water on a smaller unit at 6 lb can use under 20 lb.

How often should I add salt to my water softener?

Check the brine tank once a month and top it up when it's about a quarter full. With typical use that's one or two 40 lb bags a month for a family.

Why is my water softener using so much salt?

The usual causes are a high salt setting, a timer valve that regenerates on a fixed schedule whatever you use, a hardness setting higher than your real water, or a leak or running toilet that sends more water through. Check the setting against a fresh hardness test.

Does a lower salt setting save money?

Yes per pound, but the softener regenerates more often. Resin set to 6 lb per cubic foot softens about 3,333 grains per pound of salt, against about 2,000 at 15 lb, so yearly salt use is usually lower at the efficient setting.

How many bags of salt does a water softener use in a year?

For a family of 4 with 15 gpg water, about 15 bags of 40 lb on a metered 48,000-grain softener at 9 lb per cubic foot. On a timer set to every 7 days it's about 18 bags.

Can I use potassium chloride instead of salt?

Yes, most softeners accept it, but it takes about 13 to 15% more by weight to do the same work, and it costs several times more per bag. Raise the setting slightly when you switch.

How much does softener salt cost per year?

At $5 to $10 for a 40 lb bag, most homes spend about $50 to $150 a year on salt. Potassium chloride costs much more.