Lab units · 14 analytes
Lab unit converter, US to SI units.
Pick a test and convert between the US conventional unit and the SI unit. Covers calcium, bilirubin, testosterone, BUN-to-urea, uric acid, ferritin, vitamin B12, magnesium, glucose, lipids, creatinine, vitamin D and hemoglobin.
Convert a lab value
Result
Choose a test and enter a value in either box.
How lab unit conversion works
US laboratories usually report mass concentrations (mg/dL, ng/mL). Most of the rest of the world reports amount-of-substance concentrations (mmol/L, nmol/L). Converting between them multiplies by a fixed factor derived from the analyte's molar mass: for an mg/dL value, mmol/L = mg/dL × 10 ÷ molar mass. Each analyte has its own factor, so a factor from one test cannot be reused for another.
BUN versus urea
US reports give blood urea nitrogen (BUN), which counts only the nitrogen atoms; the rest of the world reports urea. Urea (mmol/L) = BUN (mg/dL) × 0.357. The molecule is 2.14 times heavier than its nitrogen, so urea (mg/dL) = BUN (mg/dL) × 2.14. For example a BUN of 14 mg/dL is 5.0 mmol/L urea.
Worked example
9.5 mg/dL calcium = 9.5 × 0.2495 = 2.37 mmol/L. 600 ng/dL total testosterone = 600 × 0.03467 = 20.8 nmol/L.
| Calcium (mg/dL) | mmol/L |
|---|---|
| 8.5 mg/dL | 2.12 mmol/L |
| 9 mg/dL | 2.25 mmol/L |
| 10 mg/dL | 2.50 mmol/L |
| 10.5 mg/dL | 2.62 mmol/L |
Conversion factor table
Multiply the conventional value by the factor to get the SI value; divide to go back. Factors are rounded to the digits shown.
| Test | Units | Factor | Basis |
|---|---|---|---|
| Calcium | mg/dL → mmol/L | × 0.2495 | 40.078 g/mol |
| Bilirubin | mg/dL → µmol/L | × 17.104 | 584.66 g/mol |
| Total testosterone | ng/dL → nmol/L | × 0.03467 | 288.42 g/mol |
| Urea nitrogen (BUN) to urea | mg/dL BUN → mmol/L urea | × 0.357 | 28.014 g/mol (nitrogen in urea) |
| Uric acid | mg/dL → µmol/L | × 59.48 | 168.11 g/mol |
| Ferritin | ng/mL → pmol/L | × 2.247 | 445 kDa (mass basis) |
| Vitamin B12 | pg/mL → pmol/L | × 0.7378 | 1355.4 g/mol |
| Magnesium | mg/dL → mmol/L | × 0.4114 | 24.305 g/mol |
| Glucose | mg/dL → mmol/L | × 0.05551 | 180.16 g/mol |
| Total cholesterol | mg/dL → mmol/L | × 0.02586 | 386.65 g/mol |
| Triglycerides | mg/dL → mmol/L | × 0.01129 | 885.4 g/mol (triolein) |
| Creatinine | mg/dL → µmol/L | × 88.4 | 113.12 g/mol |
| 25-hydroxyvitamin D | ng/mL → nmol/L | × 2.496 | 400.64 g/mol (25-OH D3) |
| Hemoglobin | g/dL → g/L | × 10 | mass per volume (no molar mass) |
Limits
Some tests have more than one SI convention (for example ferritin can be reported in µg/L, which equals ng/mL, or pmol/L; vitamin B12 in pmol/L or ng/L). This page uses the factors above. Ionised and total calcium use the same mass-to-molar factor but different ranges. No reference intervals are shown, because they vary by laboratory.
Sources
Molar masses from NIH PubChem; unit conventions follow standard clinical chemistry SI-conversion tables. The NIH vitamin D fact sheet corroborates the 2.5 factor for 25-OH D.
Frequently asked questions
How do I convert calcium from mg/dL to mmol/L?
Multiply by 0.2495. For example 9.5 mg/dL is 2.37 mmol/L.
How do I convert testosterone from ng/dL to nmol/L?
Multiply by 0.03467. For example 500 ng/dL is 17.3 nmol/L.
How do I convert BUN to urea?
Multiply BUN in mg/dL by 0.357 to get urea in mmol/L, or by 2.14 to get urea in mg/dL.
How do I convert bilirubin from mg/dL to µmol/L?
Multiply by 17.104. For example 1.0 mg/dL is 17.1 µmol/L.
Reference information, not medical advice
This page converts units only. It does not interpret a result, and units and reference intervals differ between laboratories. Ask the clinician who ordered the test or the reporting laboratory what a result means for you. If you are worried about a result or symptoms, contact a health professional; in an emergency call your local emergency number.