mEq/L to mg/L Converter

mEq/L

mg/L

Common Conversions

mEq/L	mg/L
0.1	0.1×AW/v
0.5	0.5×AW/v
1	AW/v
2	2×AW/v
5	5×AW/v
10	10×AW/v
20	20×AW/v
50	50×AW/v
100	100×AW/v
200	200×AW/v
500	500×AW/v
1000	1000×AW/v

Why this conversion matters in chemistry

Electrolyte-replacement IV-fluid math brings this up often. A 140 mEq/L serum sodium reading from a basic metabolic panel corresponds to 3219 mg/L of Na — the form a USP <797> compounding-pharmacy bulk-admixture worksheet writes the same quantity in. The conversion uses mg/L = mEq/L × MW/valence; for Na (MW 22.99, valence 1), the factor is 23. The mEq notation is the natural one for clinical work because it directly reflects charge balance across the cell membrane and through the kidney; mass-based mg/L is the form pharmacy compounding documents and reagent prep ledgers expect.

Formula

mg/L = (mEq/L × atomic weight) ÷ valence

Worked Examples

1 mEq/L Na⁺ (AW 23, v=1) = 23 mg/L

Sodium — the most common monovalent cation in clinical electrolyte panels.

2 mEq/L Ca²⁺ (AW 40, v=2) = 40 mg/L

Calcium — divalent, so the mEq and mg scales differ by half the atomic weight.

1 mEq/L K⁺ (AW 39.1, v=1) = 39.1 mg/L

Potassium — the second monovalent cation that dominates clinical electrolyte work.

1 mEq/L Cl⁻ (AW 35.5, v=1) = 35.5 mg/L

Chloride — the principal monovalent anion in extracellular fluid.

Frequently Asked Questions

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

mg/L = (mEq/L × atomic weight) ÷ valence. So 5 mEq/L of Ca²⁺ becomes (5 × 40) ÷ 2 = 100 mg/L. The conversion needs both the atomic weight and the valence of the ion.

What is equivalent weight?

Equivalent weight = atomic weight ÷ valence. So mg/L = mEq/L × equivalent weight. For Ca²⁺ that's 40/2 = 20; for Na⁺ it's 23/1 = 23. Memorizing the equivalent weights for the common clinical electrolytes lets the conversion happen by inspection.

When is this conversion needed?

Water-quality analysis often reports electrolytes in mEq/L while regulatory standards or reagent specs use mg/L — bridging the two is routine. Clinical contexts running mEq/L need to land in pharmacy mg/L for any compounded IV-fluid preparation calculation.