How to Convert Blood Sugar Units: mg/dL to mmol/L & Ranges
Blood sugar levels are reported in two different units depending on where you live: mg/dL (milligrams per decilitre) is common in India, the US, and many other countries, while mmol/L (millimoles per litre) is used in the UK, Canada, and much of Europe. If you're reading a study, using a glucose meter from abroad, or comparing lab results, you'll need to convert between these units. This guide provides the exact conversion formula, normal range tables in both units, and a tool that does the math for you instantly.
Why the Two Units Exist
mg/dL measures the actual mass of glucose in a volume of blood, while mmol/L counts the number of glucose molecules. The conversion factor (18.018) comes from the molecular weight of glucose (~180.16 g/mol) divided by 10 to go from litres to decilitres. So 1 mmol/L ≈ 18 mg/dL. It's a straight multiplication or division, but rounding can cause small errors. For clinical decisions, precision matters — that's where our converter helps.
- To convert mmol/L → mg/dL: multiply by 18.018 (or ≈ 18).
- To convert mg/dL → mmol/L: divide by 18.018 (or ≈ 18).
- Fasting vs post‑meal reference ranges exist in both units.
Step-by-step: Convert Your Blood Sugar Reading
- Open the Blood Sugar Converter tool.
- Enter your reading in either mg/dL or mmol/L.
- The tool instantly shows the equivalent value in the other unit with appropriate rounding.
- It also displays the reading's category (normal, pre‑diabetic, diabetic) for both fasting and random tests, so you can interpret the number immediately.
Normal, Pre‑Diabetic & Diabetic Ranges
| Test Type | Normal (mg/dL / mmol/L) | Pre‑Diabetic (mg/dL / mmol/L) | Diabetic (mg/dL / mmol/L) |
|---|---|---|---|
| Fasting | 70–99 / 3.9–5.5 | 100–125 / 5.6–6.9 | ≥ 126 / ≥ 7.0 |
| 2 hours after meal (post‑prandial) | < 140 / < 7.8 | 140–199 / 7.8–11.0 | ≥ 200 / ≥ 11.1 |
The A1C Calculator can then take multiple readings to estimate your average blood sugar over the past 2‑3 months — a more complete picture than a single finger‑stick.
Frequently Asked Questions
Why does my lab use mmol/L but my doctor says mg/dL?
Some labs in India report in mmol/L for international standardization, while clinicians often think in mg/dL. Convert using the tool to avoid confusion.
Is the conversion factor exactly 18?
No, it's 18.018. For daily use, 18 is close enough (5.6 mmol/L × 18 = 100.8, while the precise conversion gives 100.9 mg/dL). The tool uses the exact factor.
What is a "random" blood sugar test?
A random test is taken any time regardless of meals. A random reading ≥200 mg/dL (11.1 mmol/L) with symptoms suggests diabetes.
Can unit conversion affect my diagnosis?
Rounding errors could, but doctors use whole numbers and standard thresholds. Always confirm the unit on your report before comparing to reference ranges.
Is it free and private?
Yes — the tool runs entirely in your browser, free, with no sign‑up and nothing uploaded to a server.
If your blood sugar readings consistently fall in the pre‑diabetic or diabetic range, please consult a doctor for a formal diagnosis and management plan.
Try the Blood Sugar Converter