what size water softener do i need

What Size Water Softener Do I Need? (Simple Calculator)

So you have decided to get yourself a water softener! You are looking all over the internet, but very soon, you found out that selecting a softener is not as straightforward as you have thought. So, what size water softener do I need? You end up asking yourself after reading everything about grains, resins, salt, and tank.

Let me help you out:

The size of the softener is mainly determined by water hardness and water consumption in your household. When selecting a softener, you also want to pay attention to salt efficiency during the recovery and select a unit with a higher capacity than you need to maintain high efficiency.

Now, let’s dive deeper into different requirements and considerations. I have also included a simple calculator to help you out with the sizing. Note that in this article, I assume that you are looking for the whole house softener. In all honesty, requirements are similar for any type of softener.

Requirements To Get The Correct Size

Although there are plenty of different requirements that will help you select a softener, these are the questions that you need to ask yourself when sizing the softener.

  • How hard is my water?
  • What is my daily consumption? How much water do I need to soft?
  • How much salt does the softener consume?
  • Will the softener be able to handle high flow in the house?

Each of these questions is necessary to answer if you want to select a softener size that will fit your needs.

Let me help you to answer them.

Water Hardness

If you want to get the most of your water softener and properly size it, hardness is the first thing you want to measure and take it from here.

To make it easier for you to understand, the hardness is measured as the amount of minerals calcium and magnesium per gallon or liter. The higher the number of parts, the harder the water is. Simple.

In the water treatment world, there is a simple guideline to determine the level of hardness and what is considered as hard or extremely hard. Below is the table you can refer to.

Milligrams per liter (mg/l) and parts per million (ppm)Grains Per Gallon (gpg)U.S. Geological Survey Classification
<17.1 <1.0 soft
17.1 - 60 1.0 - 3.5 soft
60 - 120 3.5 - 7 moderately hard
120 - 180 7 - 10.5 hard
180> 10.5> very hard

So how can you determine the exact water hardness? To get a precise number, you will have to get your water tested. No worries, there are plenty of testing kits that are specifically designed to measure hardness.

You don’t need to do this to determine how hard your water roughly is. If all your new appliances are covered with limescale quickly, chances are that your water is very hard.

However, to select the correct softener size, it is better to know the exact hardness.

What you need to keep in mind is that various kits will tell you different results, some will measure parts per million (ppm), and milligrams per liter (mg/L) and others will measure in grains per gallon (Grain/Gal). To make your life easier, if you need to convert the value from mg/L to grains per gallon, you can divide the number by 17.1.

For example, your result tells you that you have got 134 mg/L hardness. Divide this number by 17.1, and you will get 7.84 Grains/Gal.

The bottom line is that hardness plays crucial role when selecting the size as you will see later in this post.

Now let’s have a look into daily consumption and how it affects the size of the softener you should pick.

Household Water Consumption

The amount of water you consume daily is also crucial. In fact, I would say the importance is on pair with hardness as it directly determines how much water your softener should be able to process.

The best way for you to measure the whole household usage is to write down water meter readings and check them in a week. For daily usage, you could write readings every evening for seven days and average the number.

Note that you need to write readings roughly the same time to keep the consistency.

The other way you can measure your consumption is that you can calculate it.

Although I don’t recommend it for a simple reason – accuracy.

Don’t get me wrong, you can still come up with a rough estimation, but it won’t be near as close as writing down a water meter readings.

Later in the article, I show you how I would go about selecting a softener for a family of five.

But before I can do so, let’s cover two more aspects of sizing.

Softener Efficiency

This section is a little bit tricky and technical, but I will try to make it simple and keep you awake.

I won’t go into a lot of details; instead I will try to give you the logic behind.

The efficiency of the softener can be simply described as the ratio of recovered capacity per pound of salt.

I know it sounds complicated, but in essence, it means how much of the resin the softener can recharge with one pound of salt. This is measured in grains, so how many grains you can recover during the regeneration.

Obviously, the higher the number of recharged grains, the efficiency is better, the softener drains less water and uses less salt to recover.

Now here is the problem:

The higher the capacity, the efficiency goes down, as you can see in the graph below.

softener size vs salt efficiency
Courtesy of Watertreatmentguide.com

To explain this simply, if you have a softener, let’s say with a capacity of 64,000 grains. The regeneration process will be highly efficient to recharge about 30-40% of the total capacity.

In other words, the softener will utilize salt efficiently up to 25,000 grains roughly, and after this point, the consumption of salt goes up disproportionately to regenerate the rest.

What it means for you is that to recharge 100% of the resin, you will use the extreme amount of salt.

The bottom line is that you are better off purchasing a softener with a higher initial capacity then you need and set the regeneration to recharge the required volume.

From the long term perspective, you will save more money on salt, which will recover the initial purchase cost.

Hopefully, I have made it simple to understand, but if you need some more technicalities or help, just let me know in the comments.

Softener Flow Rate

Selecting a softener based on household water usage is not the end of the story. The problem occurs with the daily water consumption spikes that happen in every single household.

Just think about it; let’s assume an average consumption of 90 gallons per person per day as an example. This is the considered average in the US.

Chances are that the most significant spikes of water usage will be during the morning hours when you are getting ready for work, having a shower and morning routine, getting kids ready for school.

Then you would use very little, or you wouldn’t use any water throughout the day as most of us are at work.

In the evening, when everyone is back home, you will see a big spike in water consumption again when we cook, kids have a shower after their afternoon sports activities, etc.

Here is the graph of how this could potentially look like.

water usage daily spikes

Now what it means is that the daily usage is not evenly distributed during the day. What it means for you,  in terms of the softener size, the softener needs to be able to handle these spikes.

This is where the water flow of the softener comes into consideration. Because multiple taps are often used within the house, softener must process a larger volume of water.

The good thing is, it is infrequent for the house to have a flow of more than 10 gallons per minute, with the standard pressure of about 50 psi.

But I would advise you to consider this and try to roughly estimate how many taps you use simultaneously in your household. By doing this exercise, you get a rough idea of the flow rate you need.

Softener Size Calculator

To make it easier for you to estimate the size of the softener, I have decided to create a simple calculator.

It is straightforward to use just fill in your water hardness, daily consumption per person, and the number of family members.

The calculator shows you the actual weekly regeneration capacity you need for your household.

As we spoke about the efficiency earlier, the calculator also considers this and by default, adds 35% extra capacity and shows you a size that you can consider.

This is to ensure that you maintain the good proportion between the salt consumption and efficiency of the unit.

What Size Water Softener For Family of 5softener for family of five

Let’s do a quick calculation how to size a softener for the family of five. I will go with the scenario of two adults and three kids.

First, what we need to do is to get our water meter readings and see our water consumption.

I will go with the standard number I have said before of 90 gallons per person per day. So we would have the following calculation 90 x 5, which is equal to 450 gallons per day for our family.

Let’s say that our family lives somewhere in Utah or Colorado, where water is very hard, often having more than 10 gpg of hardness.

Our family measured the hardness of the water at the home, and the result shows 10.5 grains per gallon.

To calculate our daily softening requirements, all we need to do is to times daily consumption with hardness. Which would look like the following: 450 x 10.5= 4,725 grains

The daily softening requirements for our family is 4,725 grains. However, we need to keep in mind how often our softener will regenerate.

General recommendation to maintain a good balance of performance and salt consumption is to keep softener to regenerate about once a week.

Considering this, we need to calculate the total grain capacity between each regeneration cycle. The formula for this is 4,725 x 7 days = 33,075 grains per week.

So the weekly softening requirement for our family is roughly 33,075 grains, but this is not all.

Remember, when I said earlier that to keep the efficiency high, we need to get a bigger softener capacity then the actual requirements are?

I will go with an extra 35% capacity for this particular example. The total size, our family would be looking at, is 33,075 x 1.35 = 44,651 gallons.

Because most softeners available on the market have standardized sizes, our family will be looking for softener with a capacity of 48,000 grains.

Usually, softeners with a bigger capacity are also able to handle those daily spikes in water usage, but just be sure to check it with the manufacturer.

Other Aspects to be Aware of

Besides covering the sizing aspect of softeners, I thought it is also important to briefly include features you might want to have in your softener.

Again, I will only cover the most important elements that usually add value to softener systems.

Type of Controller

Realistically, there are only two options for you.

  • Timed controller
  • Volume controller

The timed controller triggers regeneration at a specific time during the day, regardless of the water volume that has passed the softener. So, it would be either large volume that has passed and softener stop doing its job, or vice versa. Not a lot of water has been consumed, and there is no need for regeneration, which wastes water and salt.

This is also a cheaper type of controller.

The volume controller measures the amount of water softened and, based on this number, starts the regeneration process when the resin is actually exhausted. It generates less waste as the regeneration is done just in time when needed.

But this type is a bit more expensive.

Single vs Dual Tank

The main difference between these two types is that a single tank won’t be able to supply softened water during the regeneration phase. On the other hand, dual tank softener provides water on-demand 24/7 even while regenerating.

While the first tank regenerates, the second is still working and softening water and vice versa.

I don’t think I need to explain to you that a dual tank is not only more expensive, but also the running cost could be higher because essentially you need to maintain two softeners.

After sale Service

I believe that after-sale service is critical to keep me happy as the customer. So, don’t be afraid to ask for the type of service that is provided to you after you have bought the softener.

The buying part is the easiest, and I know some manufacturers who will charge you almost half the price of the softener only for the installation. In my eyes, this is a rip-off, and I don’t want you to get to the stage where you receive the installation bill.

The bottom line is always to see what services they offer to you.

As a final remark, I want you to remember that there are countless options for softener features like wireless connection, color touch screen, mobile phone apps, etc. These are nice to see, but they have absolutely nothing to do with the water softening, yet they move a price up heavily.

Think about whether you need an app or WiFi connection before you waste money on it.

Also, always go with renowned and trusted brands such as Fleck or Whirlpool. Don’t buy cheap softeners from brands that are very unknown as you could get yourself a good headache with it later.

You can read my selection of best water softeners, where I include both salt-based and salt-free conditioners. These are known brands that have proven themselves in quality.

Final Words

As you just saw, selecting a softener could be science if you do it yourself, but I am confident enough that with this article, you can now be sure that you will select the right unit.

Just pay close attention to the water hardness and household consumption, and you will be fine, or use the calculator that I have created specifically for this purpose.

It’s free, so make sure you take advantage of it.

As always, I would love to hear questions and tips from you on getting the correct size softener, so leave a comment below.

  • When you have been selecting a softener, did you follow the same selection process as described?
  • What do you think is the most unnecessary feature in water softeners? Why?

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5 thoughts on “What Size Water Softener Do I Need? (Simple Calculator)”

    1. Hi Mia,

      Thanks for stopping by and for you kind words, comments like this keep me going. I have noticed that many sources are quite technical and this might not be exactly what you want to know. So, I wanted to give a simple easy to understand answer, and I am so glad that I have received such a response.

      Thanks again and if you want any help simply reach out to me.


  1. Hello We have a hardness of 598
    Nitrate level of 13.9
    EC of 1150
    Total alkalinity of 620
    pH of 8.1
    Would really like to stop the scale.
    we have a water usage of 150 GPD
    2 people
    Normal peak time 7am and 8pm
    We currently use R.O. for drinking and cooking.
    What size softener would be best for our scenario?
    Thank You and Good Day

  2. Eugen,
    Thank you so much for your expertise! I haven’t thought about my water softener for 12 years, till it stopped working. I bought it used, so knew that it was time to go new. For more than a week I have been reading and researching water softeners and your site is THE BEST I’ve read on the internet. The possibilities are seemingly endless and most are ultimately trying to sell your something. You have broken down the complex and made it practical and reasonible!
    Thank you so very much!

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