mmol/L to mg/dL: Glucose Conversion Chart & Formula

To convert blood glucose from mmol/L to mg/dL, multiply by 18 (more precisely, 18.0182). To go the other way, from mg/dL to mmol/L, divide by 18. So 7.0 mmol/L equals about 126 mg/dL, and 100 mg/dL equals about 5.5 mmol/L. Both units describe the exact same thing — the concentration of glucose in your blood — just on different scales.

The two numbers can look wildly different for the same reading, which is why a value that seems alarming in one unit is perfectly ordinary in the other. This guide gives you the formula, a full two-way chart you can check at a glance, and a quick reference for which countries use which unit.

The Conversion Formula

Glucose can be measured by mass (milligrams per deciliter, mg/dL) or by molar concentration (millimoles per liter, mmol/L). Because one millimole of glucose weighs a fixed amount, a single constant converts between them:

• mmol/L → mg/dL: multiply by 18.0182 (rounding to x18 is accurate enough for everyday use)
• mg/dL → mmol/L: divide by 18.0182 (or ÷18)

Worked examples:

• 6.0 mmol/L × 18 = 108 mg/dL
• 10.0 mmol/L × 18 = 180 mg/dL
• 140 mg/dL ÷ 18 = 7.8 mmol/L
• 200 mg/dL ÷ 18 = 11.1 mmol/L

A useful sanity check: mg/dL values run in the tens and hundreds (roughly 40–400 for most readings), while mmol/L values are small, usually a single or low double-digit number (about 2–22). If a figure looks off by a factor of about eighteen, you are almost certainly comparing across units.

mmol/L to mg/dL Conversion Chart

Every value below is calculated with the 18.0182 factor and rounded to the nearest whole mg/dL. These are common readings from low to high — not target ranges. Your personal targets are set by your care team.

mg/dL to mmol/L Conversion Chart

The reverse direction, for readings reported in mg/dL. Values are divided by 18.0182 and rounded to one decimal place.

A Few Familiar Reference Points

Some numbers come up often in diabetes care. Seeing them side by side makes the two scales click. These are general reference figures from bodies such as the American Diabetes Association (ADA) and NICE/NHS — individual targets vary, and your care team sets yours.

• The common prediabetes fasting cutoff of 100 mg/dL is about 5.5 mmol/L.
• The diabetes fasting diagnostic threshold of 126 mg/dL is exactly 7.0 mmol/L.
• The ADA general post-meal goal of under 180 mg/dL is under 10.0 mmol/L.
• The lower edge often used for hypoglycemia, 70 mg/dL, is about 3.9 mmol/L.

Why the Two Charts Do Not Line Up Perfectly

If you compare the two charts closely, you will notice they are not exact mirror images. For example, 100 mg/dL converts to 5.5 mmol/L in the mg/dL chart, but 5.5 mmol/L converts back to 99 mg/dL. That single-unit gap is not an error — it is rounding. mmol/L is normally reported to one decimal place and mg/dL to a whole number, so each direction rounds to a different level of precision. The underlying values are essentially identical; the display just snaps them to the nearest reportable figure.

This is worth knowing because it means you should not chase the last digit. A reading shown as 5.5 mmol/L and one shown as 100 mg/dL are, for all practical purposes, the same blood sugar. Home glucose meters themselves carry a margin of accuracy — international standards allow a meaningful tolerance around any single reading — so a one- or two-unit difference from a hand conversion is well within the noise of normal measurement. What matters is the trend over many readings, not whether a converted number lands on an exact round figure.

Common Conversion Mistakes to Avoid

A few slips come up again and again, and most are easy to sidestep once you know to watch for them:

• Multiplying when you should divide. Going the wrong way turns a 6.0 mmol/L reading into 0.33 instead of 108 mg/dL. Remember: small number to big number means multiply; big number to small number means divide.
• Using the wrong factor. The constant for glucose is roughly 18. Other blood tests (cholesterol, for instance) use different factors, so a general-purpose converter set to the wrong analyte will give nonsense.
• Comparing a reading to a target in the other unit. This is the most consequential mistake. Seeing 7.0 next to a target written for mg/dL can look frighteningly low, when 7.0 mmol/L is actually 126 mg/dL. Always match the units before you judge a number.
• Over-precision. Reporting a converted value as 126.13 mg/dL implies an accuracy your meter does not have. Round to a whole mg/dL or one decimal mmol/L.

Which Countries Use mmol/L vs mg/dL?

Neither unit is more correct — it is a matter of regional convention, which is why travelers and people reading international guidance so often need to convert.

Use mmol/L: the United Kingdom, Ireland, Canada, Australia, New Zealand, most of Europe (including Germany, France, the Netherlands, and Scandinavia), China, and much of Africa. International scientific and clinical literature also leans toward mmol/L, the SI unit.

Use mg/dL: the United States, Germany in some everyday contexts, France, Japan, much of the Middle East, and many countries across Latin America, southern Europe, and Asia. (Some countries, including Germany, use both depending on setting, so it is always worth checking the unit printed on a meter or lab report.)

The practical takeaway: always confirm which unit a chart, meter, or clinician is using before you compare a reading to a target. A quick glance at the scale — small numbers mean mmol/L, larger numbers mean mg/dL — usually settles it.

Keeping Your Log in One Consistent Unit

Mixing units in the same record is a common source of confusion, especially if you switch meters or move between countries. GlucoLog lets you pick either mg/dL or mmol/L and keeps every reading in that unit, so your history, 7-day dashboard, and trend charts all stay on one consistent scale. If you ever need the other unit — say, to match a report format your clinic prefers — you can switch the display setting, and the app applies the conversion so you do not have to do the arithmetic by hand. GlucoLog does not measure your glucose; it records the numbers you enter and helps you see the pattern. For a step-by-step walk-through, see the units and conversion guide.

Frequently Asked Questions

Is mmol/L or mg/dL more accurate?

Neither — they measure the identical quantity on different scales, so any reading is equally valid in either unit. The only thing that matters is converting correctly (x18 or ÷18) and comparing your number to a target expressed in the same unit.

Why is the conversion factor 18 and not a round number?

The factor comes from the molecular weight of glucose. One millimole of glucose weighs about 180.16 milligrams, and mg/dL is measured per deciliter (a tenth of a liter), so the constant works out to roughly 18.0182. Rounding to 18 introduces only a tiny difference for everyday readings.

Do I need to convert my readings myself?

Usually not. Meters and apps display whichever unit you set, and clinical guidance is written for the unit common in your region. Converting is mainly useful when you are reading a chart, study, or guideline from a country that uses the other unit. When in doubt about what your numbers mean, talk to your doctor.

What number should I use in an emergency?

Do not stop to convert if you feel unwell. Symptoms — not a specific figure — are what matter in the moment. A very low reading, often described as below about 3.9 mmol/L (70 mg/dL), or a very high one can be dangerous. If you or someone else has severe symptoms such as confusion, loss of consciousness, or a reading your care team has told you to treat as urgent, seek emergency medical help right away rather than reaching for a converter.

Want to see how these numbers map onto real targets? Read our guides to normal blood sugar levels by age, fasting blood sugar range, and converting A1C to average blood sugar.