This blood sugar converter translates blood glucose between the two unit systems the world uses — mg/dL (US and others) and mmol/L (most of the rest) — with the clinical reference points that give a number meaning.
One Test, Two Dialects
The conversion is chemistry: glucose's molar mass makes mmol/L = mg/dL ÷ 18.016 (most people use 18). The US, Japan and parts of Europe report mg/dL; the UK, Canada, Australia and most of the world report mmol/L — so a "5.5" in London is a "99" in Los Angeles, and travelers with diabetes learn the factor or carry this page. For the three-month average version of the same story, see our A1C Calculator. Part of our Health Calculators collection.
Reference Points (Adults, Plasma Glucose)
| Context | mg/dL | mmol/L | Interpretation band |
|---|---|---|---|
| Fasting | 70–99 | 3.9–5.5 | Normal |
| Fasting | 100–125 | 5.6–6.9 | Prediabetes (impaired fasting glucose) |
| Fasting | ≥ 126 | ≥ 7.0 | Diabetes threshold (confirm on repeat) |
| 2 hours after a meal | < 140 | < 7.8 | Normal response |
| 2 hours after a meal | 140–199 | 7.8–11.0 | Prediabetes band |
| Random | ≥ 200 | ≥ 11.1 | Diabetes threshold with classic symptoms |
Worked Examples (Verified)
- 100 mg/dL = 5.5 mmol/L — the border between normal and prediabetes fasting, in both dialects (the widget's default)
- 126 mg/dL = 7.0 mmol/L — the fasting diabetes threshold is a rounder number in mmol/L, a hint of which system the criteria grew up in
- 7.8 mmol/L = 140 mg/dL — the 2-hour post-meal ceiling
Related Tools
- A1C Calculator — glucose as a 3-month average
- GFR Calculator — the kidney panel companion
- Health Calculators — the full collection
Frequently Asked Questions
How do I convert mg/dL to mmol/L?
Divide by 18 (precisely 18.016): 100 mg/dL = 5.5 mmol/L. Reverse: multiply mmol/L by 18 — 7.0 mmol/L = 126 mg/dL.
What is a normal blood sugar level?
Fasting: 70–99 mg/dL (3.9–5.5 mmol/L). Two hours after eating: under 140 mg/dL (7.8 mmol/L). Targets for people with diagnosed diabetes are individualized and usually looser.
Why do countries use different units?
Historical convention: mg/dL measures mass per volume; mmol/L measures molecule count per volume (the SI-style approach). The patient-facing risk is unit confusion abroad — always state the unit with the number.
Is a CGM or meter reading the same as a lab value?
Close but not identical: meters and CGMs are calibrated to report plasma-equivalent values, with allowed error around ±15% — fine for management and conversion, while diagnoses rest on laboratory plasma tests.
What does 5.5 mmol/L mean in American units?
99 mg/dL — top of the normal fasting range. Multiply any mmol/L by 18 for the mg/dL figure; the converter above does it exactly (18.016).
Is this blood sugar converter free?
Yes — free and instant, for information; interpretation of your results belongs with your care team.