Sodium and potassium are almost always reported in mmol/L everywhere, so conversion to mg/dL is mainly needed for nutrition and research. Calcium, magnesium and phosphate are reported in mg/dL in the US and mmol/L elsewhere, so those conversions matter when comparing lab reports between countries.
Converters in This Group
| Test | mmol/L → mg/dL factor | Convert | Reverse |
|---|---|---|---|
| Sodium | × 2.299 | Sodium mmol/L to mg/dL | Sodium mg/dL to mmol/L |
| Potassium | × 3.91 | Potassium mmol/L to mg/dL | Potassium mg/dL to mmol/L |
| Calcium | × 4.008 | Calcium mmol/L to mg/dL | Calcium mg/dL to mmol/L |
| Ionized Calcium | × 4.008 | Ionized Calcium mmol/L to mg/dL | Ionized Calcium mg/dL to mmol/L |
| Magnesium | × 2.431 | Magnesium mmol/L to mg/dL | Magnesium mg/dL to mmol/L |
| Phosphate | × 3.097 | Phosphate mmol/L to mg/dL | Phosphate mg/dL to mmol/L |
To convert mg/dL to mmol/L, divide by the same factor.
About These Tests
Sodium
The main salt in blood; normal is about 135–145 mmol/L. Labs almost always report sodium in mmol/L (the same number as mEq/L).
Potassium
Controls nerve and heart-muscle function; normal is about 3.5–5.0 mmol/L (equal to mEq/L).
Calcium
Total blood calcium, normally about 2.15–2.55 mmol/L (8.6–10.2 mg/dL).
Ionized Calcium
The free, active fraction of calcium, normally about 1.12–1.32 mmol/L (4.5–5.3 mg/dL).
Magnesium
Needed for muscles, nerves and heart rhythm; normal is about 0.7–1.0 mmol/L (1.7–2.4 mg/dL).
Phosphate
Reported as phosphorus; normal in adults is about 0.8–1.5 mmol/L (2.5–4.5 mg/dL).
How the Factors Are Calculated
Each factor is the molar mass of the substance (g/mol) divided by 10. Factors were last verified on 24 September 2026. Read more in our editorial policy.
Sources
- Burtis CA, Bruns DE (eds). Tietz Fundamentals of Clinical Chemistry and Molecular Diagnostics. Standard adult reference intervals; your laboratory’s ranges may differ.
- IUPAC Commission on Isotopic Abundances and Atomic Weights. Standard atomic weights (used for all molar masses).
Reference ranges vary between laboratories. Use the range printed on your own report and discuss results with your doctor.