Lab Unit Converter: Conventional and SI Units
Convert common blood test results between conventional units, such as mg/dL, and SI units, such as mmol/L, including HbA1c between percent and mmol/mol.
Why the same test has two units
Laboratories report results either in conventional units, which measure mass (such as milligrams per decilitre), or in SI units, which count molecules (such as millimoles per litre). Converting between the two uses the molecular weight of the substance being measured, so each test has its own factor.
How the factors are calculated
For each test, the SI value equals the conventional value multiplied by a unit scale and divided by the molecular weight; the molecular weights below come from PubChem, the US National Library of Medicine's chemistry database, and our build checks them against PubChem every time. Blood urea nitrogen converts to urea using the weight of urea's two nitrogen atoms, and triglycerides use triolein, the standard reference molecule.
| Test | Conventional | SI | Multiply by | Molecular weight |
|---|---|---|---|---|
| Glucose | mg/dL | mmol/L | 0.05551 | 180.16 g/mol |
| Cholesterol (total, LDL, HDL, non-HDL) | mg/dL | mmol/L | 0.02586 | 386.7 g/mol |
| Triglycerides | mg/dL | mmol/L | 0.01129 | 885.4 g/mol |
| Creatinine | mg/dL | µmol/L | 88.4 | 113.12 g/mol |
| Uric acid | mg/dL | µmol/L | 59.48 | 168.11 g/mol |
| Blood urea nitrogen (BUN) to urea | mg/dL (BUN) | mmol/L (urea) | 0.357 | 28.014 g/mol |
| Vitamin D (25-hydroxy) | ng/mL | nmol/L | 2.496 | 400.6 g/mol |
| Testosterone | ng/dL | nmol/L | 0.03467 | 288.4 g/mol |
| Cortisol | µg/dL | nmol/L | 27.59 | 362.5 g/mol |
| Vitamin B12 | pg/mL | pmol/L | 0.7378 | 1355.4 g/mol |
HbA1c: percent and mmol/mol
HbA1c is reported in percent by the US National Glycohemoglobin Standardization Program (NGSP) and in mmol/mol based on the IFCC reference method. When reference laboratories from both networks measured the same samples, the results followed NGSP % = 0.915 × IFCC % + 2.15 (r² = 0.998);1 because IFCC mmol/mol is the IFCC percentage multiplied by 10, the converter uses that equation in mmol/mol form. On this basis, 6.5% (NGSP) corresponds to 48 mmol/mol, the level that can be used to diagnose diabetes.2
What this converter leaves out
Lipoprotein(a) is not included: it is reported either as a mass (mg/dL) or as a particle concentration (nmol/L), and we have not found a validated way to convert one into the other. A conversion also changes only the units, not the meaning: reference ranges differ between laboratories, so compare your result with the range on your own report.
How we check this converter
Every time the site is built, an automated test compares our conversions with an independent implementation across 125 values for these tests, including the published 6.5% to 48 mmol/mol HbA1c pairing; the build fails if any result differs.
This converter is for convenience and education. It does not interpret results; your clinician and your laboratory's reference ranges do that.
References
- 1Hoelzel W, et al. "IFCC reference system for measurement of hemoglobin A1c in human blood and the national standardization schemes in the United States, Japan, and Sweden: a method-comparison study." Clin Chem. 2004;50(1):166-74. PubMed · DOI
- 2Marin MJ, et al. "A Hemoglobinopathy That Produces an Array of Different Hemoglobin A1c Values." J Hematol. 2024;13(3):99-103. PubMed · DOI