mEq/L To mmol/L Calculator (Potassium, Sodium, Ca2+, Mg2+, Fe3+ Charts)

Here, we are going to help you convert mEq/L to mmol/L (milliEquivalents per liter to millimoles per liter). This is a simple conversion but we do have to be aware of ion charge (+1, +2, +3, -1, -2, -3). We will demonstrate that by looking at potassium (K+), sodium (Na+), calcium (Ca2+), magnesium (Mg2+), and iron (Fe3+) ion examples.

We have prepared both mEq/L to mmol/L calculator (converts mEq/L to mmol/L right away) and 5 conversion charts (for converting 1-500 mEq/L to mmol/L for K+, Na+, Ca2+, Mg2+, Fe3+) to help you out.

Before we check the calculator, let’s clear one thing up:

Is mEq/L the same as mmol/L?

In some cases, yes, in other cases, no. Namely, equivalent (Eq) is the amount of a chemical that reacts with 1 mol of another chemical in a chemical reaction. Milliequivalents per liter and mmol per liter are both concentrations that can be converted 1-to-1 if we have 1-valent ions (such as K1+, Na1+), but we can’t do that if we have 2-valent or 3-valent ions (such as Ca2+ and Fe3+, respectively).

Quick Examples:

  • 1 mEq/L of potassium ions (K+) is equal to 1 mmol/L because it has a charge of +1.
  • 1 mEq/L of sodium ions (Na+) is equal to 1 mmol/L because it has a charge of +1.
  • 1 mEq/L of calcium ions (Ca2+) is not equal to 1 mmol/L; rather it is equal to 0.5 mmol/L because we have a 2+ charge. We need two -1 ions to react with one Ca2+ ions (2 × -1 = 1 × +2)
  • Similarly, 1 mEq/L of iron three-valent ions (Fe3+) needs to react with 3 -1 ions. That’s why 1 mEq/L of Fe3+ is equal to 0.33 mmol/L (we will look at the mEq/L to mmol/L formula to see why this is).

Here is the calculator, followed by the mEq/L to mmol/L equation (we’ll look at the math), and 5 mEq/L to mmol/L conversion charts:


Let’s solve one example to demonstrate how this online mEq/L to mmol/L calculator works:

How many mmol/L is 20 mEq/L of potassium ions (K+)?

We know we have 20 mEq/L and that potassium ion charge is +1. Thus, we insert ’20’ is the mEq/L input field, and slide the ion charge slider to ‘1’. Here is the result we get (screenshot):

meq l to mmol l for potassium ions

We can immediately see that 20 mEq/L of potassium ions (K+) is equivalent to 20 mmol/L. This is because potassium has a 1+ charge. Try to slide the ion charge slider to +2, +3, +4, or -2, -3, -4 to see how to mEq/L to mmol/L conversion changes.

Note: If you need this conversion in reverse – mmol/L to mEq/L – you can check out a similar mmol/L to mEq/L calculator here.

Example: 20 mEq/L of calcium ions (Ca2+) is equal to 10 mmol/L (since we have a +2 charge). 20 mEq/L of iron ions (Fe3+) is equal to 6.67 mmol/L (since we have 3+ charge).

meq l to mmol l for 2 valent ions such as calcium ions
When we dissolve calcium carbonate (CaCO3), we get Ca2+ ions. Since we have a 2+ ion charge (not +1 or -1 charge), the mEq/L and mmol/L are not the same.

Alright, let’s have a look under the hood of this calculator:

mEq/L To mmol/L Formula

When we look at the equation that converts milliequivalents per liter to millimoles per liter, we quickly see why the ion charge matters:

mmol/L = mEq/L / ABS(Ion Charge)

We see that, in order to convert mEq/L to mmol/L, we have to divide mEq/L concentration by ion charge (that ABS just means absolute charge; it doesn’t matter is charge is +1 or -1, key is that the ions charge is 1 regardless of +/-).

Let’s solve another example to illustrate how to use this equation. How many mmol/L is 80 mEq/L of magnesium ions (Mg2+)? We see that we have 80 mEq/L and ion charge is 2. Let’s insert both numbers in the formula like this (with the result):

mmol/L (80 mEq/L Ca2+) = 80 mEq/L / 2 = 40 mmol/L

We can see that 80 mEq/L of calcium 2+ ions is equal to 40 mmol/L. You can use the calculator above to check this result.

This is just 1 example. To help everybody out, we converted 1-500 mEq/L to mmol/L for 5 commonly used ions (K+, Na+, Ca2+, Mg2+, Fe3+), and summarized the results in 5 neat conversion charts.

We will start with the 1st potassium ions (K+) mEq/L to mmol/L chart, and will proceed with the 2nd, 3rd, 4th, and 5th charts for all the cited chemical substances:

1. Potassium Ions (K+) mEq/L To mmol/L Conversion Chart

In this 1st chart, we see that the conversion for potassium ions is dead simple (1 mEq/L = 1 mmol/L) since potassium ions have 1+ charge.

Potassium mEq/L (K+): Potassium mmol/L:
1 mEq/L K+ 1 mmol/L
2 mEq/L K+ 2 mmol/L
3 mEq/L K+ 3 mmol/L
4 mEq/L K+ 4 mmol/L
5 mEq/L K+ 5 mmol/L
10 mEq/L K+ 10 mmol/L
20 mEq/L K+ 20 mmol/L
30 mEq/L K+ 30 mmol/L
40 mEq/L K+ 40 mmol/L
50 mEq/L K+ 50 mmol/L
60 mEq/L K+ 60 mmol/L
70 mEq/L K+ 70 mmol/L
80 mEq/L K+ 80 mmol/L
90 mEq/L K+ 90 mmol/L
100 mEq/L K+ 100 mmol/L
150 mEq/L K+ 150 mmol/L
200 mEq/L K+ 200 mmol/L
250 mEq/L K+ 250 mmol/L
300 mEq/L K+ 300 mmol/L
350 mEq/L K+ 350 mmol/L
400 mEq/L K+ 400 mmol/L
450 mEq/L K+ 450 mmol/L
500 mEq/L K+ 500 mmol/L

Examples of chemical substances with potassium ions are KCl (potassium chloride) and KOH (potassium hydroxide).

2. Sodium Ions (Na+) mEq/L To mmol/L Conversion Chart

With sodium ions, we have the same 1-to-1 conversion as with the potassium ions (because the ions charge = 1):

Sodium mEq/L (Na+): Sodium mmol/L:
1 mEq/L Na+ 1 mmol/L
2 mEq/L Na+ 2 mmol/L
3 mEq/L Na+ 3 mmol/L
4 mEq/L Na+ 4 mmol/L
5 mEq/L Na+ 5 mmol/L
10 mEq/L Na+ 10 mmol/L
20 mEq/L Na+ 20 mmol/L
30 mEq/L Na+ 30 mmol/L
40 mEq/L Na+ 40 mmol/L
50 mEq/L Na+ 50 mmol/L
60 mEq/L Na+ 60 mmol/L
70 mEq/L Na+ 70 mmol/L
80 mEq/L Na+ 80 mmol/L
90 mEq/L Na+ 90 mmol/L
100 mEq/L Na+ 100 mmol/L
150 mEq/L Na+ 150 mmol/L
200 mEq/L Na+ 200 mmol/L
250 mEq/L Na+ 250 mmol/L
300 mEq/L Na+ 300 mmol/L
350 mEq/L Na+ 350 mmol/L
400 mEq/L Na+ 400 mmol/L
450 mEq/L Na+ 450 mmol/L
500 mEq/L Na+ 500 mmol/L

Examples of chemical substances with sodium ions are NaCl (sodium chloride) and NaOH (sodium hydroxide).

3. Calcium Ions (Ca2+) mEq/L To mmol/L Conversion Chart

Calcium ions are another story because they have a +2 charge. By the way, most salt water softeners use this Na+ and Ca2+ ion charge difference to fight water hardness. Here is the conversion chart for calcium ions:

Calcium mEq/L (Ca2+): Calcium mmol/L:
1 mEq/L Ca2+ 0.5 mmol/L
2 mEq/L Ca2+ 1 mmol/L
3 mEq/L Ca2+ 1.5 mmol/L
4 mEq/L Ca2+ 2 mmol/L
5 mEq/L Ca2+ 2.5 mmol/L
10 mEq/L Ca2+ 5 mmol/L
20 mEq/L Ca2+ 10 mmol/L
30 mEq/L Ca2+ 15 mmol/L
40 mEq/L Ca2+ 20 mmol/L
50 mEq/L Ca2+ 25 mmol/L
60 mEq/L Ca2+ 30 mmol/L
70 mEq/L Ca2+ 35 mmol/L
80 mEq/L Ca2+ 40 mmol/L
90 mEq/L Ca2+ 45 mmol/L
100 mEq/L Ca2+ 50 mmol/L
150 mEq/L Ca2+ 75 mmol/L
200 mEq/L Ca2+ 100 mmol/L
250 mEq/L Ca2+ 125 mmol/L
300 mEq/L Ca2+ 150 mmol/L
350 mEq/L Ca2+ 175 mmol/L
400 mEq/L Ca2+ 200 mmol/L
450 mEq/L Ca2+ 225 mmol/L
500 mEq/L Ca2+ 250 mmol/L

Examples of chemical substances with calcium ions include CaCl2 (calcium chloride), CaCO3 (calcium carbonate), CaO (calcium oxide), Ca(OH)2 (calcium hydroxide).

4. Magnesium Ions (Mg2+) mEq/L To mmol/L Conversion Chart

Magnesium ions mEq/L convert to mmol/l in the same manner as calcium ions since both have a +2 ion charge. Here is the 4th conversion chart for magnesium:

Magnesium mEq/L (Mg2+): Magnesium mmol/L:
1 mEq/L Mg2+ 0.5 mmol/L
2 mEq/L Mg2+ 1 mmol/L
3 mEq/L Mg2+ 1.5 mmol/L
4 mEq/L Mg2+ 2 mmol/L
5 mEq/L Mg2+ 2.5 mmol/L
10 mEq/L Mg2+ 5 mmol/L
20 mEq/L Mg2+ 10 mmol/L
30 mEq/L Mg2+ 15 mmol/L
40 mEq/L Mg2+ 20 mmol/L
50 mEq/L Mg2+ 25 mmol/L
60 mEq/L Mg2+ 30 mmol/L
70 mEq/L Mg2+ 35 mmol/L
80 mEq/L Mg2+ 40 mmol/L
90 mEq/L Mg2+ 45 mmol/L
100 mEq/L Mg2+ 50 mmol/L
150 mEq/L Mg2+ 75 mmol/L
200 mEq/L Mg2+ 100 mmol/L
250 mEq/L Mg2+ 125 mmol/L
300 mEq/L Mg2+ 150 mmol/L
350 mEq/L Mg2+ 175 mmol/L
400 mEq/L Mg2+ 200 mmol/L
450 mEq/L Mg2+ 225 mmol/L
500 mEq/L Mg2+ 250 mmol/L

Examples of chemical substances with magnesium ions include MgCl2 (magnesium chloride) and Mg(OH)2 (magnesium hydroxide).

4. Iron Ions (Fe3+) mEq/L To mmol/L Conversion Chart

Now, iron ions can have a +2 or +3 charge (for FeO and Fe2O3, respectively). Here is a mEq/L to mmol/L chart for trivalent iron ions (Fe3+):

Iron mEq/L (Fe3+): Iron mmol/L:
1 mEq/L Fe3+ 0.33 mmol/L
2 mEq/L Fe3+ 0.67 mmol/L
3 mEq/L Fe3+ 1 mmol/L
4 mEq/L Fe3+ 1.33 mmol/L
5 mEq/L Fe3+ 1.67 mmol/L
10 mEq/L Fe3+ 3.33 mmol/L
20 mEq/L Fe3+ 6.67 mmol/L
30 mEq/L Fe3+ 10 mmol/L
40 mEq/L Fe3+ 13.33 mmol/L
50 mEq/L Fe3+ 16.67 mmol/L
60 mEq/L Fe3+ 20 mmol/L
70 mEq/L Fe3+ 23.33 mmol/L
80 mEq/L Fe3+ 26.67 mmol/L
90 mEq/L Fe3+ 30 mmol/L
100 mEq/L Fe3+ 33.33 mmol/L
150 mEq/L Fe3+ 50 mmol/L
200 mEq/L Fe3+ 66.67 mmol/L
250 mEq/L Fe3+ 83.33 mmol/L
300 mEq/L Fe3+ 100 mmol/L
350 mEq/L Fe3+ 116.67 mmol/L
400 mEq/L Fe3+ 133.33 mmol/L
450 mEq/L Fe3+ 150 mmol/L
500 mEq/L Fe3+ 166.67 mmol/L

We hope that with the calculator, formula, and these 5 conversion charts, you are now fully equipped to tack any mEq/L to mmol/L conversion. Remember: The ion charge is the key for all of such conversion. If you need any help from our side, you can use the comment section below, give us a few numbers and chemical substance, and we can do some math together.

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