Milliequivalents/L to mmol/L Converter

mEq/L

mmol/L

Common Conversions

mEq/L	mmol/L
0.1	0.1/v
0.5	0.5/v
1	1/v
2	2/v
5	5/v
10	10/v
20	20/v
50	50/v
100	100/v
140	140/v
200	200/v
500	500/v

Why this conversion matters in chemistry

Critical-care electrolyte-replacement math hits this regularly. A 5 mEq/L calcium-replacement IV admixture is 2.5 mmol/L on the modern clinical-chemistry report — the divalent Ca²⁺ scales by half between the two notations. The arithmetic: the equivalent definition: one equivalent is one mole of charges, leaving 1/valence per equivalent. The mEq notation reflects charge balance directly and is the natural form for clinical reporting; mmol/L is the SI form increasingly preferred internationally. In practice you reach for it when a US clinical electrolyte panel needs to align with an SI-unit international guideline.

Formula

mmol/L = mEq/L ÷ valence

Worked Examples

140 mEq/L Na⁺ (valence 1) = 140 mmol/L

Normal serum sodium — monovalent, so the values match exactly.

5 mEq/L Ca²⁺ (valence 2) = 2.5 mmol/L

Normal serum calcium — divalent, so mmol is half of mEq.

4 mEq/L K⁺ (valence 1) = 4 mmol/L

Normal serum potassium — another monovalent identity case.

2 mEq/L Mg²⁺ (valence 2) = 1 mmol/L

Normal serum magnesium — divalent, half-scale conversion.

Frequently Asked Questions

How do I convert mEq/L to mmol/L?

Divide by valence. For monovalent ions (Na⁺, K⁺, Cl⁻) the values are identical. For divalent (Ca²⁺, Mg²⁺) divide by 2; for trivalent (Al³⁺) divide by 3.

What is an equivalent?

One equivalent is the amount of substance that supplies or reacts with one mole of charges. So 1 mmol of Ca²⁺ delivers 2 mEq of charge — the doubling falls cleanly out of the divalent ion's two units of charge per ion.

Is mEq/L still used?

Yes, widely in US clinical practice for serum electrolytes — Na⁺, K⁺, Cl⁻, HCO₃⁻ all report in mEq/L on a basic metabolic panel. International labs and SI-aligned guidelines have moved toward mmol/L; the conversion is the bridge between conventions.