If you have ever compared a US lab report with a European or Asian one, you have hit the wall: one side prints your blood sugar as 100, the other as 5.5, and neither number looks familiar on its own. The two units — milligrams per deciliter (mg/dL) and millimoles per liter (mmol/L) — measure the same concentration, but they use different systems, and the conversion factor is not the same for every test. This calculator converts any blood-test result from mg/dL to mmol/L and picks the right factor for the analyte you are checking.
Why the Factor Is Not Always 18
The most famous conversion, for blood glucose, is 18.016: 1 mmol/L of glucose equals 18.016 mg/dL. That number comes from glucose's molar mass (about 180.16 grams per mole) divided by ten. But cholesterol has a molar mass near 386.7 g/mol, so its factor is 38.67. Triglycerides are even larger molecules, with a factor around 88.57. If you use the glucose factor on a cholesterol reading, a "200" that should be 5.17 mmol/L comes out as 11.1 — a number that looks alarming on a lipid panel. Picking the right analyte is the whole point of this tool.
How to Use
- Enter the Reading (mg/dL) — the number printed on your US-style lab report or glucose meter.
- Choose the What are you converting? substance. The default is glucose (blood sugar). Pick cholesterol for total, HDL or LDL numbers, triglycerides for the lipid-panel line, uric-acid for gout panels, or bilirubin for liver tests.
- If your lab report uses a non-standard analyte, switch to custom and type the Custom Factor from your lab's reference table.
- Read the result card: the Reading (mmol/L) is the converted value, and the Conversion Factor Used confirms which math was applied.
Examples
Example 1 — Fasting glucose. A fasting glucose of 100 mg/dL converts to 100 / 18.016 = 5.55 mmol/L. This is the textbook normal-to-borderline value, and it lines up with an HbA1c of about 5.7% that sits right on the prediabetes threshold.
Example 2 — Total cholesterol. A total cholesterol of 200 mg/dL converts to 200 / 38.67 = 5.17 mmol/L, which is the boundary between desirable and borderline-high on most US lipid guidelines.
Example 3 — Triglycerides. A triglyceride reading of 150 mg/dL converts to 150 / 88.57 = 1.69 mmol/L — the cut point where triglycerides start to be considered elevated.
Example 4 — Reverse direction. If a Canadian friend tells you their glucose is 6.0 mmol/L, multiply by 18.016 to get 108 mg/dL. The same multiplication works in reverse for cholesterol: 5.0 mmol/L × 38.67 ≈ 193 mg/dL.
Common Conversion Factors at a Glance
| Analyte | mg/dL → mmol/L factor | 100 mg/dL becomes |
|---|---|---|
| Glucose (blood sugar) | 18.016 | 5.55 mmol/L |
| Total / HDL / LDL cholesterol | 38.67 | 2.59 mmol/L |
| Triglycerides | 88.57 | 1.13 mmol/L |
| Uric acid | 16.81 | 5.95 mmol/L |
| Bilirubin | 58.47 | 1.71 mmol/L |
These factors are the standard values used by clinical laboratories in the US, Canada, the UK, and most of Europe. If your lab report lists a slightly different factor — for example 18.02 instead of 18.016 for glucose — the difference is a rounding error under 0.1% and will not change how you interpret the result.
Reading the Two Side by Side
US labs report mg/dL for historical reasons — the convention was already widespread when the metric system was adopted in medicine. Most of the rest of the world reports mmol/L, which is a concentration unit that works naturally with molar chemistry. When you travel, read a foreign study, or compare your own results from a past US test with a current overseas one, you need to translate. The two values are interchangeable; only the unit changes.
A useful sanity check: normal fasting glucose is roughly 70–99 mg/dL in the US, or 3.9–5.5 mmol/L elsewhere. Total cholesterol under 200 mg/dL is under 5.17 mmol/L. If your converted number lands in a wildly different range than you expected, double-check that you picked the right analyte — using the glucose factor on a cholesterol number is the single most common mistake people make on these converters.
FAQ
How do you convert mg/dL to mmol/L?
Divide the mg/dL value by the conversion factor for that specific analyte. For glucose, divide by 18.016; for cholesterol, divide by 38.67; for triglycerides, divide by 88.57. The factor is the molar mass of the molecule divided by ten, so each analyte has its own number — there is no universal mg/dL-to-mmol/L factor.
Why is the glucose factor 18.016 and not 18?
Glucose has a molar mass of about 180.16 grams per mole. To convert milligrams per deciliter to millimoles per liter you divide by 180.16 and multiply by 10, which simplifies to dividing by 18.016. The rounded factor 18 is fine for everyday estimates, but 18.016 is the value used by clinical meters and lab instruments, and it is what this calculator uses by default.
Is 100 mg/dL the same as 5.5 mmol/L?
Yes. 100 mg/dL divided by 18.016 equals 5.55 mmol/L, which rounds to 5.5 or 5.6 on most meters. This is the classic normal fasting glucose value and the number most blood-sugar conversion tables center on. If your meter shows 5.5 mmol/L after a fast, you are sitting right at the boundary that corresponds to an HbA1c of about 5.7%.
How do I convert cholesterol from mg/dL to mmol/L?
Divide by 38.67. For example, total cholesterol of 200 mg/dL becomes 5.17 mmol/L, and an LDL of 100 mg/dL becomes 2.59 mmol/L. HDL uses the same 38.67 factor because it is also a lipoprotein reported in the same concentration units — only triglycerides and glucose need their own, separate factors.
What is the conversion factor for triglycerides?
Triglycerides use a factor of about 88.57, which is larger because triglyceride molecules are heavier than cholesterol. A triglyceride reading of 150 mg/dL converts to 1.69 mmol/L, and 200 mg/dL converts to 2.26 mmol/L. If you accidentally apply the glucose factor, the result will look nearly five times too high.
Can I use this calculator for creatinine or bilirubin?
Bilirubin is included in the built-in list (factor about 58.47). Creatinine is usually reported in μmol/L rather than mmol/L, so it is not on the default list — switch the substance to custom and type the factor printed on your specific lab report to convert any other analyte not listed here.
Disclaimer
This mg/dL to mmol/L calculator is provided for informational purposes only and is not medical advice. It is a unit-conversion tool, not a diagnostic device. Converted values are approximations rounded for display; your official lab report and meter readings are the authoritative numbers. Always discuss your results with a qualified healthcare professional who can interpret them in the context of your full medical history, medications, and clinical picture. Do not use these converted numbers to self-adjust insulin, cholesterol medication, or any prescription without your doctor's guidance.