Convert mg to mEq or mEq to mg for potassium, KCl, sodium, calcium, magnesium or bicarbonate, or mmol to mEq, with a custom molar mass and valence.
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mEq Formula
The mEq calculator uses the relationship between milliequivalents, milligrams, millimoles, molecular weight, and valence. The formula depends on the calculation type you select.
- mEq = milliequivalents
- mg = milligrams
- mmol = millimoles
- valence = absolute ionic charge number (a positive integer). For salts, use the equivalents of one specified ionic component per formula unit
- molecular weight = molecular weight or atomic weight, commonly in g/mol, which is numerically equivalent to mg/mmol
To calculate mEq from mg, the calculator multiplies the milligram amount by the valence and divides by molecular weight.
To calculate mg from mEq, it rearranges the same formula and multiplies mEq by molecular weight, then divides by valence.
To calculate mEq from mmol, it multiplies mmol by valence because each millimole contributes one or more equivalents depending on charge.
To calculate mmol from mEq, it divides mEq by valence.
Common Valences and Atomic Weights
These approximate values apply to the named elemental ions. Use the exact chemical species and hydration state corresponding to the mass. For NaCl or KCl presets, mEq refers separately to the sodium/potassium or chloride component; do not sum cation and anion equivalents. Salt mass is not elemental-ion mass. This is chemical unit conversion, not dosing advice.
| Ion | Symbol | Typical Valence | Atomic Weight |
|---|---|---|---|
| Sodium | Na+ | 1 | 22.99 |
| Potassium | K+ | 1 | 39.10 |
| Calcium | Ca2+ | 2 | 40.08 |
| Magnesium | Mg2+ | 2 | 24.31 |
| Chloride | Cl- | 1 | 35.45 |
mEq Conversion Reference
| Substance | Valence | Approximate mg per 1 mEq |
|---|---|---|
| Sodium | 1 | 22.99 mg |
| Potassium | 1 | 39.10 mg |
| Calcium | 2 | 20.04 mg |
| Magnesium | 2 | 12.15 mg |
Example Problems
Example 1: Convert mg to mEq
You have 390 mg of potassium. Potassium has a valence of 1 and an atomic weight of 39.10.
The result is about 9.97 mEq.
Example 2: Convert mmol to mEq
You have 5 mmol of calcium. Calcium has a valence of 2.
The result is 10 mEq.
FAQ
What is the difference between mmol and mEq?
Millimoles measure the amount of substance. For a specified ion, milliequivalents express chemical amount multiplied by absolute ionic charge number; they are not an electrical charge measurement in coulombs. For ions with a valence of 1, mmol and mEq are numerically the same. For ions with a valence of 2, the mEq value is twice the mmol value.
What valence should you enter?
Enter the charge number of the ion as a positive value. For sodium, potassium, chloride, and bicarbonate, use 1. For calcium and magnesium, use 2. Do not enter the plus or minus sign.
Why is molecular weight needed for mg conversions?
Milligrams measure mass, while mEq depends on chemical amount and charge. Molecular weight connects mass to millimoles. Once the millimoles are known, valence converts the amount to milliequivalents.
