PonyatnoHow it's calculated
Mass units (mg/dL, µg/dL, ng/dL, ng/mL, pg/mL) are converted to molar units (mmol/L, µmol/L, nmol/L, pmol/L) using the substance's molar mass M in g/mol. One rule covers all of them: × 10 / M for matching prefixes (mg/dL → mmol/L, µg/dL → µmol/L, ng/dL → nmol/L); × 10,000 / M when the molar unit is one step smaller (mg/dL → µmol/L, µg/dL → nmol/L, ng/dL → pmol/L); × 1000 / M for ng/mL → nmol/L and pg/mL → pmol/L. Converting back means multiplying by M with the same factor.
For example, glucose has M = 180.16 g/mol, so mg/dL is divided by about 18; creatinine has M = 113.12, so mg/dL is multiplied by about 88.4; vitamin D has M = 400.64, so ng/mL is multiplied by about 2.5.
The molar masses are the same ones the Ponyatno app uses when it reads lab reports. Results are rounded: molar units to 2 decimals, mg/dL, µg/dL, ng/dL and pg/mL to 1 decimal.
What to know
Why the units differ
Most of Europe, the UK, Canada and Australia report in SI units — mmol/L, µmol/L, nmol/L. The US and some private labs use mg/dL and ng/mL. The same number means very different things: a glucose of "90" is normal in mg/dL but impossible in mmol/L.
What cannot be converted this way
Molar-mass conversion only works for substances with a defined chemical formula. Enzymes (ALT, AST, GGT in U/L) and hormones reported in international units (TSH, LH, FSH, prolactin, insulin, hCG in IU or mIU) cannot be converted like this: their unit is tied to an assay standard, not to mass.
Cholesterol uses one factor for total, LDL and HDL; bilirubin one for total and direct; calcium one for total and ionised. Vitamin D here means 25-hydroxyvitamin D, the usual blood test.
Convert the reference range too
Only compare a result with a reference range in the same units. If you convert the value, convert the range limits from your report as well — they differ between labs and methods, and the range printed next to your result is the one that applies.
This calculator is a reference tool, not a diagnosis. Laboratory ranges differ, and the result depends on your health, medicines and other tests. Discuss it with your doctor.
FAQ
How do I convert glucose from mg/dL to mmol/L?
Divide by 18 (more precisely, multiply by 10 and divide by 180.16). For example, 100 mg/dL ≈ 5.55 mmol/L. To go back, multiply by 18.
How do I convert cholesterol from mmol/L to mg/dL?
Multiply by about 38.7. The factor is the same for total, LDL and HDL cholesterol. Triglycerides use a different factor (about × 88.6), so pick them separately.
Vitamin D: ng/mL or nmol/L?
1 ng/mL of 25-OH vitamin D ≈ 2.5 nmol/L, so 30 ng/mL ≈ 75 nmol/L. Check which units your report's reference range uses before comparing.
Why does my result differ slightly from another converter?
Usually rounding or a slightly different molar mass. A difference in the second decimal does not change what the result means.
Can I convert TSH or insulin here?
Not with this method. TSH, LH, FSH and other hormones in IU are not directly linked to molar mass. Insulin from pmol/L to µU/mL uses a conventional factor — it is built into the HOMA-IR calculator.
Sources
Formulas and cut-offs follow clinical guidelines — see sources below.
- Young DS. Implementation of SI units for clinical laboratory data. Ann Intern Med. 1987;106(1):114–129.
- Conversion factors are the same as in Ponyatno's lab-report analysis (based on each substance's molar mass).