Blood Sugar Conversion Calculator
Convert blood sugar levels between mg/dL and mmol/L.
Includes reference ranges for fasting, post-meal, and A1C equivalents.
Blood sugar unit conversion switches between milligrams per deciliter (mg/dL), used in the United States, and millimoles per liter (mmol/L), used in most other countries. The conversion factor is a fixed constant.
Conversion Formulas:
mmol/L = mg/dL / 18.02
mg/dL = mmol/L × 18.02
The factor 18.02 represents the molar mass of glucose (180.2 g/mol) divided by 10. Because glucose is a single compound with a known molecular weight, this conversion is exact — not an approximation.
Worked example: US reading: 126 mg/dL (fasting) International: 126 / 18.02 = 6.99 mmol/L → 7.0 mmol/L
International reading: 5.5 mmol/L US equivalent: 5.5 × 18.02 = 99.1 → 99 mg/dL
Clinical reference ranges (fasting blood glucose):
| Category | mg/dL | mmol/L |
|---|---|---|
| Normal | 70–99 | 3.9–5.5 |
| Prediabetes | 100–125 | 5.6–6.9 |
| Diabetes | 126+ | 7.0+ |
| Hypoglycemia | Below 70 | Below 3.9 |
| Severe hypoglycemia | Below 54 | Below 3.0 |
HbA1c to average glucose conversion:
Estimated Average Glucose (mg/dL) = (HbA1c × 28.7) − 46.7
Example: HbA1c of 7.0% → (7.0 × 28.7) − 46.7 = 200.9 − 46.7 = 154 mg/dL average
Practical context:
- Post-meal glucose normally peaks 60–90 minutes after eating and returns to baseline within 2 hours
- Target post-meal peak for non-diabetics: below 140 mg/dL (7.8 mmol/L)
- CGM devices (Dexterity, Libre) display readings in the units set by the user’s device region