GPG To mg/L Of CaCO3 Calculator (Water Hardness Conversion)

If you want to convert water hardness GPG to mg/L of CaCO3, you are in the right place. We will explain exactly how to convert these water hardness units (GPG or Grains Per Gallon to mg/L of CaCO3 or milligrams per Liter of calcium carbonate). To help you out, we have also prepared these 2 key resources, namely:

  1. GPG to mg/L Calculator. This is simple; just insert GPGs and the calculator will automatically convert them to mg/L of CaCO3.
  2. GPG to mg/L Chart. We have calculated how many mg/L CaCO3 are GPGs ranging from 0.1 GPG to 50 GPG, and summarized all the results in the conversion chart. You will also see colored rows in the chart, based on the water hardness categorization: soft water (0-60 ppm) is denoted with this green color, moderately hard water (61-120 ppm) with this light blue color, hard water (121-180 ppm) with this blue color, and very hard water (181+ ppm) with this dark blue color.

Now, for the conversion, we only need this GPG to mg/L of CaCO3 formula:

Water Hardness (mg/L Of CaCO3) = 17.118 × GPG 

This means that 1 GPG is equal to 17.118 mg/L of CaCO3. Before we check the calculator and chart, let’s solve this quick example:

How many mg/L of CaCO3 is 10 GPG? We just insert 10 GPG in the equation like this:

Water Hardness (mg/L Of CaCO3) = 17.118 × 10 GPG = 171.18 mg/L of CaCO3

We see that 10 GPG is equal to 171.18 mg/L of CaCO3. This is categorized as “hard water”; more about water hardness categorization (soft, moderately hard, hard, and very hard water) in the chart below.

Here is the GPG to mg/L of CaCO3 converter you can freely use:

GPG To mg/L Of CaCO3 Calculator


Example: Let’s say you want to convert 6.1 GPG to mg/L of CaCO3. Just slide the GPG slider in the calculator to ‘6.1‘, and you get the result:

6.1 GPG is equal to 104.42 mg/L of CaCO3. This is considered “moderately hard” water; you would need a bit of water softening to get to “soft water”.

Here is the full conversion chart with 0.1 GPG to 50 GPG converted to mg/L of CaCO3:

GPG To mg/L Of CaCO3 Conversion Chart

Grains Per Gallon (GPG): mg/L Of CaCO3:
0.1 GPG 1.71 mg/L Of CaCO3
0.2 GPG 3.42 mg/L Of CaCO3
0.3 GPG 5.14 mg/L Of CaCO3
0.4 GPG 6.85 mg/L Of CaCO3
0.5 GPG 8.56 mg/L Of CaCO3
0.6 GPG 10.27 mg/L Of CaCO3
0.7 GPG 11.98 mg/L Of CaCO3
0.8 GPG 13.69 mg/L Of CaCO3
0.9 GPG 15.41 mg/L Of CaCO3
1 GPG 17.12 mg/L Of CaCO3
1.5 GPG 25.68 mg/L Of CaCO3
2 GPG 34.24 mg/L Of CaCO3
2.5 GPG 42.79 mg/L Of CaCO3
3 GPG 51.35 mg/L Of CaCO3
3.5 GPG 59.91 mg/L Of CaCO3
4 GPG 68.47 mg/L Of CaCO3
4.5 GPG 77.03 mg/L Of CaCO3
5 GPG 85.59 mg/L Of CaCO3
5.5 GPG 94.15 mg/L Of CaCO3
6 GPG 102.71 mg/L Of CaCO3
6.5 GPG 111.27 mg/L Of CaCO3
7 GPG 119.83 mg/L Of CaCO3
7.5 GPG 128.39 mg/L Of CaCO3
8 GPG 136.94 mg/L Of CaCO3
8.5 GPG 145.50 mg/L Of CaCO3
9 GPG 154.06 mg/L Of CaCO3
9.5 GPG 162.62 mg/L Of CaCO3
10 GPG 171.18 mg/L Of CaCO3
11 GPG 188.30 mg/L Of CaCO3
12 GPG 205.42 mg/L Of CaCO3
13 GPG 222.53 mg/L Of CaCO3
14 GPG 239.65 mg/L Of CaCO3
15 GPG 256.77 mg/L Of CaCO3
16 GPG 273.89 mg/L Of CaCO3
17 GPG 291.01 mg/L Of CaCO3
18 GPG 308.12 mg/L Of CaCO3
19 GPG 325.24 mg/L Of CaCO3
20 GPG 342.36 mg/L Of CaCO3
21 GPG 359.48 mg/L Of CaCO3
22 GPG 376.60 mg/L Of CaCO3
23 GPG 393.71 mg/L Of CaCO3
24 GPG 410.83 mg/L Of CaCO3
25 GPG 427.95 mg/L Of CaCO3
26 GPG 445.07 mg/L Of CaCO3
27 GPG 462.19 mg/L Of CaCO3
28 GPG 479.30 mg/L Of CaCO3
29 GPG 496.42 mg/L Of CaCO3
30 GPG 513.54 mg/L Of CaCO3
35 GPG 599.13 mg/L Of CaCO3
40 GPG 684.72 mg/L Of CaCO3
45 GPG 770.31 mg/L Of CaCO3
50 GPG 1855.90 mg/L Of CaCO3

To help you determine if your water is hard or not, we at Waternity Lab always color these conversion charts in accordance with the water hardness scale categorization. Namely, you can see that:

  • Soft water contains 0 to 59.91 mg/L of CaCO3.
  • Moderately hard water contains 59.92 to 119.83 mg/L of CaCO3.
  • Hard water contains 119.83 to 171.18 mg/L of CaCO3.
  • Very hard water contains more than 171.19 mg/L of CaCO3.

Hopefully, this explains well how to convert GPG to mg/L of calcium carbonate. If something is unclear, or you would like for us to offer you a hand, you can use the comment section below, give us some numbers, and we will help you out.

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