Convert mg/L To PPM (CaCO3, CaO, Ca2+): 3 Calculators + 3 Charts

We can express water hardness in several mg/L units. We can talk about mg/L of CaCO3 (calcium carbonate), mg/L of CaO (calcium oxide), and mg/L of Ca2+ (calcium ions). Most often, however, water hardness is expressed in PPMs (Parts Per Million). That’s why it’s useful to convert water hardness mg/L to PPM (milligrams per liter to parts per million), and we will show you how to do it.

Here, we provide a look at each of these 3 conversion in turn (pick the one you need), namely:

  1. mg/L CaCO3 to PPM Calculator, Example, Chart. In the calculator, you insert mg/L of CaCO3 and get the PPM equivalent automatically. We also explain how to convert mg/L of CaCO3 manually, provide a 200 mg/L CaCO3 to PPM example, and feature a chart where we converted 0-1,000 mg/L CaCO3 to PPM.
  2. mg/L CaO to PPM Calculator, Example, Chart. Insert mg/L of CaO and get the PPM equivalent automatically. We solve a 100 mg/L CaO to PPM example and feature a conversion chart (0-500 mg/L CaO to PPM).
  3. mg/L Ca2+ to PPM Calculator, Example, Chart. This 3rd calculator converts Ca2+ to PPM. Again, we provide an example (150 Ca2+ to PPM), and a 0-500 Ca2+ to PPM conversion chart.

Note: All 3 calculators will categorize inserted water hardness as “Soft Water”, “Moderately Hard Water”, “Hard Water”, and “Very Hard Water”. We also colored all the 3 charts with these colors (“Soft Water” is this light green color, and so on) so that you immediately know how hard your water is.

Let’s start with CaCO3 conversion (calcium carbonate), and then we will proceed to the 2nd CaO conversion (calcium oxide) and the 3rd Ca2+ conversion (calcium ions):

Convert mg/L CaCO3 To PPM (1st Conversion)

Converting mg/L CaCO3 to PPM is the simplest possible conversion. This is basically because of this relationship:

1 mg/l CaCO3 = 1 PPM

Essentially, 1 mg/L of CaCO3 is equal to 1 PPM. Quantiatevely, mg CaCO3/L is the same unit as PPM. That means that 15 mg/L CaCO3 is 15 PPM, 30 mg/L CaCO3 is 30 PPM, and so on.

Just to make this clear, we have created a conversion calculator and conversion chart for CaCO3 (things become more interesting for CaO to PPM, and Ca2+ to PPM conversions):

You can also check our this calculation in reverse with our PPM to mg/L calculator here.

mg/L CaCO3 To PPM Chart (1st Chart)

You can see that this conversion is crazy simple. This conversion chart is color-coded; we begin with “soft” water up to 60 mg/L CaCO3 (60 PPM), and follow with “moderately hard” water from 61 to 120 mg/L CaCO3 (61 to 120 PPM), “hard” water from 121 to 180 mg/L CaCO3 (121 to 180 PPM). Water that contains more than 180 mg/L CaCO3 (180 PPM) is categorized as “very hard” water.

Here is the full chart:

mg/L CaCO3 (Calcium Carbonate): PPM (Parts Per Million):
0 mg/L CaCO3 0 PPM
1 mg/L CaCO3 1 PPM
5 mg/L CaCO3 5 PPM
10 mg/L CaCO3 10 PPM
15 mg/L CaCO3 15 PPM
20 mg/L CaCO3 20 PPM
25 mg/L CaCO3 25 PPM
30 mg/L CaCO3 30 PPM
35 mg/L CaCO3 35 PPM
40 mg/L CaCO3 40 PPM
45 mg/L CaCO3 45 PPM
50 mg/L CaCO3 50 PPM
60 mg/L CaCO3 60 PPM
70 mg/L CaCO3 70 PPM
80 mg/L CaCO3 80 PPM
90 mg/L CaCO3 90 PPM
100 mg/L CaCO3 100 PPM
110 mg/L CaCO3 110 PPM
120 mg/L CaCO3 120 PPM
130 mg/L CaCO3 130 PPM
140 mg/L CaCO3 140 PPM
150 mg/L CaCO3 150 PPM
160 mg/L CaCO3 160 PPM
170 mg/L CaCO3 170 PPM
180 mg/L CaCO3 180 PPM
190 mg/L CaCO3 190 PPM
200 mg/L CaCO3 200 PPM
250 mg/L CaCO3 250 PPM
300 mg/L CaCO3 300 PPM
350 mg/L CaCO3 350 PPM
400 mg/L CaCO3 400 PPM
450 mg/L CaCO3 450 PPM
500 mg/L CaCO3 500 PPM
550 mg/L CaCO3 550 PPM
600 mg/L CaCO3 600 PPM
650 mg/L CaCO3 650 PPM
700 mg/L CaCO3 700 PPM
750 mg/L CaCO3 750 PPM
800 mg/L CaCO3 800 PPM
850 mg/L CaCO3 850 PPM
900 mg/L CaCO3 900 PPM
950 mg/L CaCO3 950 PPM
1000 mg/L CaCO3 1000 PPM

Let’s now proceed to the more interesting mg/L CaO and mg/L Ca2+ conversions to PPM:

Convert mg/L CaO To PPM (2nd Conversion)

1 mg/l CaO = 1.7848 PPM. This is all we need to know here; mg/L CaO (milligrams of calcium oxide) is a bigger unit than PPM. We can write mg/L CaO to PPM conversion formula like this:

PPM = mg/L CaO × 1.7848

Quick Example: How many PPM is 200 mg/L of CaO? Simple, just insert that ‘200’ in the equation like this:

PPM (200 mg/L CaO) = 200 mg/L CaO × 1.7848 = 356.96 PPM

You can do mg CaCO3/L to PPM conversion manually, or just use this calculator that does it automatically (much easier):


Here is how the mg/L CaO to PPM calculator works:

Say you want to convert 150 mg/L CaO to PPM. Just slide the mg/L CaO slider to ‘150’, and you get this result immediately:

convert mgl cao to ppm (1)

You can see right away that 150 mg/L CaO is equal to 267.72 PPM. On top of that, we see that 150 mg/L CaO or 267.72 is considered “Very Hard” water.

Here is a helpful conversion chart for the CaO conversion:

mg/L CaO To PPM Chart (2nd Chart)

You can see the same color-coding for “Soft”, “Moderately Hard”, “Hard”, and “Very Hard” water in this chart as well:

mg/L CaO (Calcium Oxide): PPM (Parts Per Million):
0 mg/L CaO 0 PPM
1 mg/L CaO 1.78 PPM
5 mg/L CaO 8.92 PPM
10 mg/L CaO 17.85 PPM
15 mg/L CaO 26.77 PPM
20 mg/L CaO 35.70 PPM
25 mg/L CaO 44.62 PPM
30 mg/L CaO 53.54 PPM
35 mg/L CaO 62.47 PPM
40 mg/L CaO 71.39 PPM
45 mg/L CaO 80.32 PPM
50 mg/L CaO 89.24 PPM
60 mg/L CaO 107.09 PPM
70 mg/L CaO 124.94 PPM
80 mg/L CaO 142.78 PPM
90 mg/L CaO 160.63 PPM
100 mg/L CaO 178.48 PPM
110 mg/L CaO 196.33 PPM
120 mg/L CaO 214.18 PPM
130 mg/L CaO 232.02 PPM
140 mg/L CaO 249.87 PPM
150 mg/L CaO 267.72 PPM
160 mg/L CaO 285.57 PPM
170 mg/L CaO 303.42 PPM
180 mg/L CaO 321.26 PPM
190 mg/L CaO 339.11 PPM
200 mg/L CaO 356.96 PPM
250 mg/L CaO 446.20 PPM
300 mg/L CaO 535.44 PPM
350 mg/L CaO 624.68 PPM
400 mg/L CaO 713.92 PPM
450 mg/L CaO 803.16 PPM
500 mg/L CaO 892.40 PPM

From this you can see that:

  • “Soft” water has below or equal to 33.62 mg/L CaO (60 PPM) content.
  • “Moderately Hard” water contains between 33.63 mg/L and 67.23 mg/L CaO (61-120 PPM).
  • “Hard” water contains between 67.24 mg/L to 100.85 mg/L CaO (121-180 PPM) content.
  • “Very Hard” water contains more than 100.86 mg/L CaO (180+ PPM) content.

Now, let’s look at calcium ions (Ca2+):

Convert mg/L Ca2+ To PPM (3rd Conversion)

Compared to PPM, mg/L Ca2+ (calcium ions) is a larger unit. Namely, 1 mg/L Ca2+ is equal to 2.497253 PPM (we could say it’s about 2.5 PPM, but all those decimal point make the conversion more precise).

That means we can write the mg/L Ca2+ to PPM formula like this:

PPM = mg/L Ca2+ × 2.497253

Quick Example: How many PPM is 50 mg/L Ca2+? If we insert ’50’ in the equation above and calculate like this:

PPM (50 mg/L Ca2+) = 50 mg/L Ca2+ × 2.497253 = 124.86 PPM

This is a manual conversion (that can be a bit lengthy). An easier way to convert mg/L Ca2+ is to use the following 3rd calculator we prepared:

Alright, let’s solve one example with this calculator:

Say you want to know how many PPM is 40 mg/L Ca2+. Just slide the slider to ’40’, and you get this result right away:

mgl calcium ions to ppm

We can quickly see that 40 mg/L Ca2+ is equal to 99.89 PPM. You can also see that this water hardness is categorized as “Moderately Hard” water.

Here is the full chart where we have converted 0-500 mg/L Ca2+ to PPM:

mg/L Ca2+ To PPM Chart (3rd Chart)

mg/L Ca2+ (Calcium Ions): PPM (Parts Per Million):
0 mg/L Ca2+ 0 PPM
1 mg/L Ca2+ 2.50 PPM
5 mg/L Ca2+ 12.49 PPM
10 mg/L Ca2+ 24.97 PPM
15 mg/L Ca2+ 37.46 PPM
20 mg/L Ca2+ 49.95 PPM
25 mg/L Ca2+ 62.43 PPM
30 mg/L Ca2+ 74.92 PPM
35 mg/L Ca2+ 87.40 PPM
40 mg/L Ca2+ 99.89 PPM
45 mg/L Ca2+ 112.38 PPM
50 mg/L Ca2+ 124.86 PPM
60 mg/L Ca2+ 149.84 PPM
70 mg/L Ca2+ 174.81 PPM
80 mg/L Ca2+ 199.78 PPM
90 mg/L Ca2+ 224.75 PPM
100 mg/L Ca2+ 249.73 PPM
110 mg/L Ca2+ 274.70 PPM
120 mg/L Ca2+ 299.67 PPM
130 mg/L Ca2+ 324.64 PPM
140 mg/L Ca2+ 349.62 PPM
150 mg/L Ca2+ 374.59 PPM
160 mg/L Ca2+ 399.56 PPM
170 mg/L Ca2+ 424.53 PPM
180 mg/L Ca2+ 449.51 PPM
190 mg/L Ca2+ 474.48 PPM
200 mg/L Ca2+ 499.45 PPM
250 mg/L Ca2+ 624.31 PPM
300 mg/L Ca2+ 749.18 PPM
350 mg/L Ca2+ 874.04 PPM
400 mg/L Ca2+ 998.90 PPM
450 mg/L Ca2+ 1123.76 PPM
500 mg/L Ca2+ 1248.63 PPM

From this you can see that:

  • “Soft” water has below or equal to 24.03 mg/L Ca2+ (60 PPM) content.
  • “Moderately Hard” water contains between 24.04 mg/L and 48.05 mg/L Ca2+ (61-120 PPM).
  • “Hard” water contains between 48.06 mg/L to 72.09 mg/L Ca2+ (121-180 PPM) content.
  • “Very Hard” water contains more than 72.10 mg/L Ca2+ (180+ PPM) content.

You can also check this conversion in reverse with our PPM to mg/L CaCO3 and Ca2+ calculator here.

With all these 3 conversion calculators and chart to PPM (from mg/L CaCO3, mg/L CaO, and mg/L Ca2+), you are now fully equipped to make this conversion. If you need any help from us, you can use the comments section, give us a few numbers, and we can do a bit of math for you.

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