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):

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).

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.

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):

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:

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:

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⁺):

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.