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MasterMath

Blood Glucose Converter

Converts blood glucose between milligrams per decilitre and millimoles per litre, the two units the same thing is measured in depending on the country, and gives the matching A1c.

Equivalent

—

Equivalent—
In mg/dl—
In mmol/l—
Equivalent A1c if this were the average—
Conversion factor—
Fasting reference—

How this was worked out

    Indicative result. A single figure diagnoses nothing. Diagnosing diabetes requires repeating the test and reading it alongside the rest of the clinical picture.

    The formula

    mmol/l = mg/dl ÷ 18.0182

    Where it comes from

    The two units measure the same concentration with a different yardstick: mg/dl is mass per volume and mmol/l is amount of substance per volume. The bridge between them is glucose's molecular weight, 180.16 grams per mole, divided by ten to go from decilitres to litres, which gives the 18.0182 in the conversion. The United States and much of Latin America use mg/dl; the United Kingdom and most of Europe use mmol/l.

    How to work it out by hand

    1. If you have mg/dl and want mmol/l, divide by 18.0182
    2. If you have mmol/l and want mg/dl, multiply by 18.0182
    3. For a quick mental estimate, just divide or multiply by 18
    4. The equivalent A1c comes from (glucose + 46.7) ÷ 28.7

    What is worth knowing

    The A1c shown here assumes that reading were your average glucose over the last two or three months, and a single measurement is not. A normal fasting glucose sits perfectly happily alongside a high A1c if the post-meal spikes are large. The equivalence comes from the ADAG study and has its own margin. The most widely used fasting references are below 100 mg/dl normal, 100 to 125 prediabetes, and 126 or more diabetes on two determinations.

    Frequently asked questions

    Why are there two units?

    Country tradition. mg/dl measures mass and mmol/l amount of substance; the bridge is glucose's molecular weight.

    Can I just divide by 18?

    For a mental estimate, yes. The exact factor is 18.0182 and the difference is tenths.

    Is the A1c shown mine?

    Only if that reading were your average glucose over two or three months. A single measurement is not.

    What fasting values are normal?

    Below 100 mg/dl, or 5.6 mmol/l. From 100 to 125 is called prediabetes, and 126 or more diabetes if repeated.

    Does the same factor work for cholesterol?

    No. Every substance has its own molecular weight and therefore its own conversion factor.