Blood Sugar (Glucose) Converter: mg/dL to mmol/L
Convert Blood Sugar Units (mg/dL and mmol/L)
TL;DR: This page converts blood glucose (blood sugar) between mg/dL and mmol/L. The relationship is linear: mmol/L = mg/dL ÷ 18.0156 and mg/dL = mmol/L × 18.0156. A common mental check: 100 mg/dL ≈ 5.6 mmol/L.
Introduction: Why blood sugar units differ
Blood glucose is reported in different units depending on region and laboratory conventions. In the United States (and a few other countries), glucose is commonly reported as milligrams per deciliter (mg/dL), which is a mass concentration. In much of Europe, Canada, Australia, and many other regions, glucose is reported as millimoles per liter (mmol/L), which is a molar concentration (number of glucose molecules in a volume).
If you travel, read international research, use apps built for different markets, or compare lab results with CGM/glucometer screenshots from someone in another country, you will often need to convert units to interpret values correctly. Misreading units can make a normal number look dangerously high (or low), so conversion clarity matters.
What the converter does (and does not do)
- Does: Convert a numeric glucose value between mg/dL and mmol/L using the standard glucose molecular-weight factor.
- Does not: Diagnose diabetes, interpret your personal targets, or replace medical advice. “Normal” ranges vary by context (fasting vs. post-meal, pregnancy, illness, medications, etc.).
Conversion formulas
The conversion uses the molecular weight of glucose (≈ 180.156 g/mol). Because mg/dL is a mass-per-volume unit and mmol/L is a mole-per-volume unit, the constant 18.0156 appears in the conversion.
Formulas:
- mg/dL → mmol/L: divide by 18.0156
- mmol/L → mg/dL: multiply by 18.0156
MathML:
Entering a reading
Type the glucose number exactly as your meter, CGM app, or lab report shows it, then tell the converter which unit that number is already in. If your reading came from a US meter it is almost certainly mg/dL; a reading with a decimal like 5.5 or 7.2 is almost always mmol/L. Press Convert and the result line shows both a rounded value (the way a device would display it) and an exact two-decimal value so you can see how much rounding shifted the last digit.
The Swap units button flips the starting unit and re-runs the conversion on whatever number you already typed, which is handy when you realize you picked the wrong direction. One habit worth keeping: mmol/L values live in single or low double digits (roughly 2 to 30 in real life), while mg/dL values run in the tens to low hundreds. If a converted number lands wildly outside those ranges, you almost certainly converted the wrong way.
Two conversions worked through
A US meter reading of 100 mg/dL
Dividing by the glucose factor gives 100 ÷ 18.0156 = 5.551…, so 100 mg/dL is about 5.6 mmol/L. This is the pair worth memorizing: whenever someone quotes a fasting figure near 100 in one system, its counterpart sits right around 5.6 in the other.
A European lab result of 7.0 mmol/L
Going the other way, multiply: 7.0 × 18.0156 = 126.1…, which rounds to 126 mg/dL. That number is not a coincidence — 7.0 mmol/L and 126 mg/dL are the same value expressed two ways, which is why both show up as the fasting diabetes-diagnosis line in guidelines written for different regions.
Common conversions (quick reference)
This table is handy for quick comparisons (values rounded to 1 decimal for mmol/L and to the nearest whole number for mg/dL):
| mg/dL | mmol/L | Notes (contextual, not medical advice) |
|---|---|---|
| 70 | 3.9 | Often cited as a low threshold in many guidelines; targets vary. |
| 80 | 4.4 | Common fasting-range value for many people. |
| 90 | 5.0 | Typical “around 5.0 mmol/L” reference point. |
| 100 | 5.6 | Often used in articles and examples. |
| 110 | 6.1 | Sometimes discussed in impaired fasting glucose contexts. |
| 126 | 7.0 | Common diagnostic threshold used in some contexts (confirm with clinician). |
| 140 | 7.8 | Frequently referenced post-meal/OGTT-related number in resources. |
| 180 | 10.0 | Common post-meal target threshold in some diabetes education materials. |
Interpreting results (important context)
Conversion tells you the same measurement in a different unit; it does not change what the number means clinically. Interpretation depends on when the glucose was measured and how it was measured:
- Timing: fasting, before meals, 1–2 hours after meals, during illness, overnight, after exercise, etc.
- Device type: lab plasma glucose vs. capillary fingerstick meter vs. CGM (continuous glucose monitor). These can differ systematically and by lag time.
- Rounding: many displays round mmol/L to 0.1 and mg/dL to whole numbers, so small differences are normal.
Limitations & assumptions
- Unit conversion only: This is a math tool, not medical advice and not a diagnostic device.
- Glucose factor: Uses 18.0156, appropriate for glucose conversions between mg/dL and mmol/L.
- Rounding: Display rounding can slightly change the last digit. Internally, calculations use floating-point arithmetic.
- Input constraints: Negative values are rejected. Extremely large values may be valid mathematically but are unusual clinically.
- Context varies: “Normal” or “target” ranges depend on fasting status, pregnancy, age, comorbidities, and clinician guidance.
Common questions about glucose units
Why is the conversion factor 18.0156?
It comes from glucose’s molecular weight (≈180.156 g/mol) and the relationship between deciliters and liters. This yields the standard factor used to convert mg/dL ↔ mmol/L for glucose.
Is 5.5 mmol/L the same as 99 mg/dL?
Approximately. 5.5 mmol/L × 18.0156 ≈ 99.1 mg/dL, typically shown as 99 mg/dL.
Why do some charts show slightly different conversions?
Differences usually come from rounding (e.g., rounding mmol/L to one decimal) or using a shortened factor (18 instead of 18.0156).
Can I use this for ketones or other lab values?
No. The 18.0156 factor is specific to glucose. Other analytes have different molecular weights and different conversion factors.
Does this apply to plasma glucose and blood glucose meters?
The unit conversion applies to the number itself regardless of source, but meters/CGMs and lab tests can differ. Always interpret results in the context of the measurement method.
Arcade Mini-Game: Blood Sugar (Glucose) Converter: mg/dL to mmol/L Calibration Run
Use this quick arcade run to practice separating useful scenario inputs from common planning mistakes before you rely on the calculator output.
Start the game, then use your pointer or arrow keys to catch useful inputs and avoid bad assumptions.