Blood Glucose Conversion Calculator
Written by Thierno Sadou Diallo, formula verified per our methodology • Last checked on 9/10/2026
Blood glucose converts between mg/dL and mmol/L with the factor 18.016, derived from the molar mass of glucose. A blood glucose of 100 mg/dL, the normal fasting reference value, corresponds to about 5.55 mmol/L.
Explanation
The concentration of glucose in the blood (blood glucose) is expressed in two units depending on the country: the milligram per deciliter (mg/dL), used notably in the United States, and the millimole per liter (mmol/L), used in most other countries, including the United Kingdom and Canada. The conversion factor between the two (18.016) follows directly from the molar mass of glucose (about 180.16 g/mol): since one mole of glucose weighs 180.16 grams, one millimole weighs 180.16 milligrams, which fixes the exact ratio between a mass measurement (mg/dL) and an amount-of-substance measurement (mmol/L). Two widely documented medical reference points allow this factor to be checked: a fasting blood glucose of 100 mg/dL, considered normal, corresponds to about 5.55 mmol/L, and the diabetes diagnostic threshold set at 126 mg/dL by the World Health Organization corresponds to about 7.0 mmol/L — two values that recur constantly in international medical literature. As with the absorbed dose conversion, this is a purely arithmetic conversion between two units of measurement, never a medical interpretation of the result obtained. Any interpretation of a blood glucose value should be done by a healthcare professional.
Example: converting 100 mg/dL to mmol/L
Inputs
Value: 100. Starting unit: mg/dL. Target unit: mmol/L.
Calculation
100 mg/dL ÷ 18.016 ≈ 5.55 mmol/L.
Result
A blood glucose of 100 mg/dL equals about 5.55 mmol/L.
Frequently asked questions
Why don't the United States and most other countries use the same unit?
It is a historical convention difference: countries that use the International System of Units for clinical chemistry express blood concentrations in amount of substance (mmol/L), while the United States has kept an expression in mass per volume (mg/dL), more intuitive but less consistent with other biological assays expressed in mmol/L.
Can this calculator tell me whether my blood glucose is normal?
No, this calculator only performs a mathematical conversion between two units, without interpreting the result. Interpreting a blood glucose value (fasting, after a meal, as part of diabetes screening) depends on the context of the measurement and must be done by a healthcare professional, the only person qualified to assess an individual situation.
Is the conversion factor always exactly 18.016?
This factor follows from the molar mass of glucose, a well-established physicochemical constant; some sources round it to 18 or 18.02 to simplify a mental calculation, which introduces a negligible difference (less than 0.1%) on most common clinical values. To assess the impact of a food on blood glucose rather than convert a blood measurement, see our glycemic load calculator.