Free Blood Sugar Converter

Divide the mg/dL value by 18.0182. For example, 90 mg/dL = 5.0 mmol/L.

Normal fasting blood sugar is 70-99 mg/dL (3.9-5.5 mmol/L). 100-125 mg/dL is pre-diabetic range.

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To go from mmol/L to mg/dL, multiply the reading by 18.0182. For example, 7.0 mmol/L becomes about 126 mg/dL, and 5.5 mmol/L works out to roughly 99 mg/dL. This is simply the reverse of the mg/dL-to-mmol/L conversion, which divides by the same constant. mmol/L is the standard in the UK, Canada, Australia, and most of Europe, while mg/dL is used in the United States, so you often need this direction when reading an American meter or lab report from abroad. Doing it by hand risks slips that matter, since a small error can move a value across a category line. Type your mmol/L figure into the converter, choose that as your input unit, and it returns the mg/dL value instantly, with a Swap button to flip directions and a copy button for your log.

The two units describe the same glucose level but count it differently. Milligrams per deciliter (mg/dL) measures the mass of glucose in a fixed volume of blood, which is why it produces larger numbers like 90 or 126. Millimoles per liter (mmol/L) counts the number of glucose molecules in that volume, giving smaller numbers like 5.0 or 7.0. Neither is more correct; they are just different conventions adopted by different countries, with the US using mg/dL and much of the rest of the world using mmol/L. Because the scales differ by a factor of about 18, mixing them up is a genuine safety issue: 7 is normal in mmol/L but a dangerous low in mg/dL. Paste a reading into the converter and it shows both units side by side, so you always know which scale you are reading.

HbA1c, or glycated hemoglobin, reflects your average blood sugar over roughly the past two to three months rather than a single moment, so clinicians use it to track control over time. It is reported as a percentage, and the American Diabetes Association grades it in three bands: under 5.7% is normal, 5.7 to 6.4% is pre-diabetic, and 6.5% or higher falls in the diabetic range. A higher percentage means your average glucose has been running high. This tool estimates HbA1c from an average glucose value you enter using the widely cited Nathan formula, HbA1c (%) = (average mg/dL + 46.7) / 28.7, so an average of 120 mg/dL gives about 5.8%. Because it is built from an average you supply, treat it as an estimate; a laboratory test is more accurate. Enter your average reading in the HbA1c tab to see your band.

The line between the two comes down to threshold ranges, and fasting and post-meal readings have separate cutoffs. For fasting glucose, 100 to 125 mg/dL (5.6 to 6.9 mmol/L) is the pre-diabetic range, while 126 mg/dL (7.0 mmol/L) and above sits in the diabetic range. Measured two hours after a meal, 140 to 199 mg/dL (7.8 to 11.0 mmol/L) is pre-diabetic and 200 mg/dL (11.1 mmol/L) or higher is diabetic. Pre-diabetes means blood sugar is higher than normal but not yet diabetic, and lifestyle changes can often delay or prevent type 2 diabetes. These are population reference points, not personal targets, so your own doctor may set different goals. Enter a reading and the converter labels it against these exact ranges automatically.

Your blood sugar naturally rises after you eat as carbohydrates are digested into glucose, then falls again as insulin moves that glucose into your cells, so a healthy reading two hours after a meal is expected to be higher than a fasting one. That is why the reference ranges differ: normal fasting glucose is 70 to 99 mg/dL (3.9 to 5.5 mmol/L), while a normal two-hour post-meal reading is anything under 140 mg/dL (7.8 mmol/L). Comparing a post-meal number against fasting cutoffs, or vice versa, can make a perfectly healthy reading look alarming. Always note whether a value was taken fasting or after eating before judging it. This converter shows both fasting and two-hour post-meal ranges together, so you can match your reading to the correct context at a glance.