What Size Water Softener For Family Of 5? (Calculator + Examples)

You have a family of 5. You want to protect the piping, washing machines, etc., from hard water. You already figured out you need a water softener. Let’s address the first key question you need to solve here: How big a water softener do you need for a family of 5?

You have many different sizes of water softeners with 24,000-grain, 36,000-grain, 48,000-grain, 64,000-grain capacities, etc. Which one is the best for a family of 5? We are going to help you figure out how many grains water softener you need for a 5-member household with 3 very helpful resources, namely:

  1. Family of 5 water softener size calculator. Here you just insert water usage, water hardness, and potential iron content, and you get the 5-family water softener grain capacity automatically.
  2. Three examples. We looked into 3 different 5 member households, and calculated water softener size for them. All the examples are featured below the calculator.
  3. All-encompassing 5-family member water softener size chart. In this chart, we have calculated the size of water softener needed for 5 member families with very low, very high water usage, and all in between. We also accounted for very soft vs. very hard water hardness in these households (we do presume 0 PPM iron content).

Let’s start with the 3 basic metrics you need to size water softeners for any family size adequately. Basically, there are only 3 key factors that determine a water softener size:

  1. How much water do you use per month? You can get this info from your monthly water bill. The US Geological Survey in 2015 determined that we use 83 gallons of water per person per day. Based on this, 5 member household uses, on average, 415 gallons of water per day, and 12,450 gallons of water per month.5 family household water usage per month
  2. How hard is your water? The harder the water, the bigger water softener you will need (more calcium ions (Ca2+) and magnesium ions (Ca2+) that need to be removed). We can measure our water hardness with a TDS meter, or get this info from our water provider (measurement is more accurate, obviously). We need to express the water hardness in GPG (Grains Per Gallon).
  3. Iron content. We need to measure the concentration of iron ions (Fe2+). Many household have don’t have iron in their water (0 PPM). If you have any, however, we need to add 5 GPG of water hardness for every 1 PPM of iron to adequately adjust the size of water softener to account for iron as well.

Once we get both of these data points, you can just insert them in the calculator below, and you will get a good estimate of what size water softener you need for a 5-member family.

Don’t worry if this sounds a bit complicated. We will present 3 different 5-member family examples and water softener sizing (complete with explanation) below this calculator:


Let’s start with the 1st example to illustrate how to use this calculator. Here is the message we got:

“Hi, Melissa here from Nebraska. We are a family of 5, 2 boys, 1 girl. I’ve checked our water bill; we used 9450 gallons last month. I’m concerned because we are using very hard well water. The measurement has shown 9.5 GPG water hardness. No iron. How many grain water softener should we get?”

Alright, we have all the data here we need to help Melissa out. In the calculator, we should slide the 1st gallon/month slider to ‘9,450’, the 2nd water hardness slider to ‘9.50’, and we can leave iron content at 0 PPM. Here is the result:

calculating water softener size for 5 member household

We can quickly see that we need a water softener with 27,927 grain capacity for this family of 5. The closest water softener sizes are 24,000-grain and 30,000-grain units. Here, it’s better to opt for 30,000 grain capacity unit just to be sure we have enough.

Obviously, getting bigger 36,000-grain or 42,000-grain units would be wasting money, and you can have regen cycle problems with the oversized units (42,000-grain units would definitely be a regrettable choice, for example).

Note: We have also created a similar calculator for a family of 4. You can check it in our article titled “What Size Water Softener For Family Of 4” here.

Let’s look at 2 examples of 5 member homes with high water hardness and iron content:

2nd Example: 5 Member Family With Very Hard Water And Iron Content

This is a family with about 11,500 gallons/month of water usage. This is quite average for a 5 family home. However, this household has very hard 12.9 GPG water hardness. In addition, we are also dealing with 1.0 PPM iron content. Surely, such a home will need a big water softener, but how big exactly?

We can use the calculator above to determine that (you can do that right now). But just to illustrate how to calculate this manually, let’s use the following water softener size formula:

Water Softener Size (Grains) = (Water Hardness (GPG) + Iron Content (PPM) × 5) × Monthly Water Usage (Gallons/Month) × 0.2333 / 0.75

I know, the formula looks a bit complex, that’s why using the calculator is much easier. Nonetheless, let’s just put the numbers in this snake of an equation to calculate the water softener size this 5-member family need like this:

Water Softener Size (Grains) = (12.9 GPG + 1 PPM × 5) × 11,500 Gallons/Month × 0.2333 / 0.75 = 64,033 Grain Capacity

We can see that this home needs a 64,033-grain capacity water softener. In this case, we simply opt for a 64,000-grain unit.

If you check with the calculator above, you can see that it gives you the same result. You can read all about how to calculate the size of water softeners properly here.

3rd Example: Family Of 5 With 200 PPM Water Hardness

Now, in a lot of cases, the water hardness is not measured in GPG (Grains Per Gallon). Rather, we most commonly measure water hardness in PPM (Parts Per Million).

Let’s look at how this is relevant in our 3rd example:

A family of 5 uses only 6,000 gallons of water per month. The measured water hardness is 200 PPM, and the measured iron content is 0.5 PPM. How to determine water softener size if we have water hardness expressed in GPG?

Well, the calculator and the formula above both use GPG water hardness, right? To determine the water softener size, we thus have to convert 200 PPM to GPG. You can do that with this PPM to GPG converter, or even by consulting water hardness PPM scale with GPG scale here.

Using the PPM to GPG converted, we see that 200 PPM is equal to 11.68 GPG. We can round this up to 11.70 GPG, and insert all the data we have in the calculator. Here is what we get:

5 family home with high water hardness water softener sizing

We see that we would need a 26,503-grain unit here. We again have the 24,000-grain vs 30,000-grain dilemma here. Now, the safe choice would be a 30,000-grain unit because kids grow up, and they usually need more water than when they are little.

If you want to save costs a bit, you can also opt for a 24,000-grain unit, and start regent cycle every 6 days, instead of the standard 7-day regen cycle.

Now that we understand how to figure out all this water softener sizing, let’s look at a summarized chart with recommended water softener sizes for families of 5:

5-Family Member Water Softener Size Chart

Here we vary water usage from very low for a 5 family household (4,000 gallons/month) to very high (18,000 gallons/month). We also vary water hardness from 6 GPG (moderately hard water) to 16 GPG (very hard water). We presume 0 PPM iron content. Here is the full chart:

5 Member Family: 6 GPG 8 GPG 10 GPG 12 GPG 14 GPG 16 GPG 18 GPG
4,000 Gallons/Month 8,000-Grain 10,000-Grain 14,000-Grain 16,000-Grain 18,000-Grain 20,000-Grain 24,000-Grain
6,000 Gallons/Month 12,000-Grain 16,000-Grain 20,000-Grain 24,000-Grain 27,000-Grain 30,000-Grain 36,000-Grain
8,000 Gallons/Month 16,000-Grain 20,000-Grain 24,000-Grain 30,000-Grain 36,000-Grain 40,000-Grain 46,000-Grain
10,000 Gallons/Month 18,000-Grain 24,000-Grain 30,000-Grain 36,000-Grain 44,000-Grain 50,000-Grain 56,000-Grain
12,000 Gallons/Month 24,000-Grain 30,000-Grain 36,000-Grain 44,000-Grain 54,000-Grain 60,000-Grain 68,000-Grain
14,000 Gallons/Month 24,000-Grain 36,000-Grain 44,000-Grain 54,000-Grain 60,000-Grain 68,000-Grain 78,000-Grain
16,000 Gallons/Month 30,000-Grain 40,000-Grain 50,000-Grain 60,000-Grain 70,000-Grain 80,000-Grain 90,000-Grain
18,000 Gallons/Month 36,000-Grain 44,000-Grain 54,000-Grain 68,000-Grain 78,000-Grain 90,000-Grain 100,000-Grain

You can use this chart for general direction. It’s best to use the calculator above, but this chart gives you a good idea how big water softener you need for a family of 5 people.

We hope this helps you to take care of your home and your family. If you need a bit of help determining the size of water softener you need, you can use the comment section below, give us a few numbers, and we can do a bit of math for you.

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