How do I convert Sodium from mg/dL to mmol/L?

mmol/L = mg/dL × 0.4349. For example, 300 mg/dL equals 130 mmol/L.

How many mmol/L are 300 mg/dL?

300 mg/dL equal 130 mmol/L (Sodium).

Electrolytes & minerals

mmol/L = mg/dL × 0.4349

Enter a value in any unit and all other units fill in.

mg/dL mmol/L = mEq/L

mg/dL → mmol/L	mmol/L = mg/dL × 0.4349
mmol/L → mg/dL	mg/dL = mmol/L × 2.299

Highlighted: values inside the adult reference range.

310.4 – 333.4 mg/dL = 135 – 145 mmol/L

Source: MedlinePlus (NLM): Sodium blood test · Last reviewed: 2026-10-14