Water Hardness PPM To dH Calculator (+ Conversion Chart)

In the US, we primarily use PPM units for water hardness. dH or degrees of Hardness (also known as dGH or German degrees) is used internationally. In some cases, you will need to convert PPM to dH.

To help you out, we have all you need to make this conversion, namely:

  1. PPM To dH Calculator. Basically, just insert PPM, and you get dH.
  2. PPM to dH Conversion Chart. We have converted PPM from 0 to 1000 PPM into dH. The chart is also color-coded: Soft water (0-60 ppm) is marked with this green color, moderately hard water (61-120 ppm) is marked with light blue color, hard water (121-180 ppm) is marked with this blue color, and very hard water (181+ ppm) is marked with this dark blue color.
  3. Water Hardness PPM To dH Chart. This is a chart that will tell you how many dH (and PPM) does soft, moderately hard, hard, and very hard water have.
water hardness ppm scale and conversion to dh
To protect your piping and water-using appliances, you should decrease the water hardness below 60 PPM or 3.37 dH.

Here are the hard water units we are converting:

  • PPM or Part Per Million is a unit of water hardness equal to 1 mg/L of calcium carbonate (CaCO3).
  • dH or degree of Hardness (also referred to as the degree of General Hardness (dGH) or German degree) is a unit of water hardness equal to 10 mg/L of calcium oxide (CaO).

Obviously, we are looking at mg/L in both cases, but at different dissolved solids (CaCO3 for PPM, CaO for dH).

That’s why we need to use this PPM to dH conversion formula:

dH = PPM / 17.848

Basically, to convert PPM to dH, we have to divide PPM by a 17.848 factor.

Example: How many dH is 1 PPM water hardness? We just insert this into the equation and calculate the result like this:

dH (1 PPM) = 1 / 17.848 = 0.056 dH

As we can see, 1 PPM is equal to 0.056 dH.

This is just an example for 1 dH. For all other conversions, you can use the following calculator (and consult the chart below the calculator). At the end, you will also be able to compare the calculated dH with a water hardness scale to determine how hard water you have:

PPM To dH Calculator


Let’s say we want to convert 60 PPM to dH using this calculator. You slide the slider to ’60’ and get the result immediately: 60 PPM is equal to 3.36 dH.

Here is the full conversion chart where we converted 0 to 1000 PPM into dH:

PPM To dH Chart

PPM (Parts Per Million): dH (degrees of Hardness or German Degrees):
0 PPM 0.056 dH
1 PPM 1.78 dH
5 PPM 0.28 dH
10 PPM 0.56 dH
15 PPM 0.84 dH
20 PPM 1.12 dH
25 PPM 1.40 dH
30 PPM 1.68 dH
35 PPM 1.96 dH
40 PPM 2.24 dH
45 PPM 2.52 dH
50 PPM 2.80 dH
60 PPM 3.36 dH
70 PPM 3.92 dH
80 PPM 4.48 dH
90 PPM 5.04 dH
100 PPM 5.60 dH
110 PPM 6.16 dH
120 PPM 6.72 dH
130 PPM 7.28 dH
140 PPM 7.84 dH
150 PPM 8.40 dH
160 PPM 8.96 dH
170 PPM 9.52 dH
180 PPM 10.09 dH
190 PPM 10.65 dH
200 PPM 11.21 dH
250 PPM 14.01 dH
300 PPM 16.81 dH
350 PPM 19.61 dH
400 PPM 22.41 dH
450 PPM 25.21 dH
500 PPM 28.01 dH
550 PPM 30.82 dH
600 PPM 33.62 dH
650 PPM 36.42 dH
700 PPM 39.22 dH
750 PPM 42.02 dH
800 PPM 44.82 dH
850 PPM 47.62 dH
900 PPM 50.43 dH
950 PPM 53.23 dH
1000 PPM 56.03 dH

If you need to convert PPM to dH, you can just look at this chart.

Example: How many dH is 100 PPM? Simple. Just look at this chart and you have the result: 100 PPM is equal to 5.60 dH. This is considered moderately hard water (hence the light blue color in the chart).

Let’s look at the water hardness chart for PPM and dH to get an idea how many PPM or dH is hard water:

Water Hardness PPM Chart

Classification Hardness (PPM) degrees of Hardness (dH)
Soft 0 – 60 0 – 3.37
Moderately hard 61 – 120 3.38 – 6.74
Hard 121 – 180 6.75 – 10.11
Very hard 181 Or More 10.12 Or More

As you can see, you should have below 60 PPM or below 3.38 dH for soft water. Very hard water starts at 181 PPM or more or at 10.12 dH or more.

Hopefully, using the PPM to dH calculator, chart, and consulting this hard water chart, will help you determine how hard your water is and by how much PPM or dH you should decrease the water hardness for your water to be considered soft and safe to use.

If you have any questions or would like for us to calculate water hardness for you, you can use the comment section below, give us some numbers, and we’ll help you out.

Thank you.

2 thoughts on “Water Hardness PPM To dH Calculator (+ Conversion Chart)”

  1. my calculation is as follows – 371ppm = 20.79dH (very Hard)

    what to do for softer water?

    we have a new ISpring water softner.

    • Hi Brian, 371 ppm is still very hard, yes. If you want to get soft water, you should bring that down below 60 ppm, and water softeners are the best way to do that. That iSpring water softener doesn’t seem to be doing the job, though. There might be a problem wit the softener itself, it may have lower-than-needed capacity, or you might have a very hard water to begin with.

      The first things you should do is troubleshoot and test if the water softener is working fine. It might be that there is a problem there.


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