Blood Sugar Unit Converter
A single reading, from a meter or a finger-prick test.
Converted using 1 mmol/L = 18.0182 mg/dL, which comes from the molar mass of glucose. Verified 5 August 2026. This tool converts units only — it does not interpret a reading. What a number means depends on when it was taken, your circumstances and your treatment, which is a conversation for your doctor or diabetes team.
Convert blood glucose between mmol/L and mg/dL, and HbA1c between mmol/mol and percent. Different countries use different units for both, so anyone reading foreign guidance, using an imported meter, or comparing notes with someone abroad ends up needing this.
How it works
Both conversions are fixed relationships, not approximations.
Glucose is measured either as a concentration of molecules (mmol/L) or as a weight per volume (mg/dL). Converting between them means going through the molar mass of glucose, 180.156 g/mol, which gives a factor of18.0182. Multiply mmol/L by it for mg/dL; divide to come back.
HbA1c is different. The older DCCT percentage and the newer IFCC mmol/mol measure the same thing on different scales, related bymmol/mol = (10.93 × %) − 23.5. It is worth noting this is a straight line with an offset, not a simple multiplication, so you cannot convert it in your head the way you can with glucose.
Worked example
A fasting reading of 7.0 mmol/L converts to 126 mg/dL. Those two figures are quoted as the diabetes diagnostic threshold in their respective countries, which is a useful check that the conversion is working — they are the same number expressed two ways, not two different standards.
On the HbA1c side, 48 mmol/mol and 6.5% are similarly the same value in the two systems. A UK patient told their HbA1c is 53 will find American material discussing the identical result as 7.0%.
Common questions
Why are there two different units for blood sugar?
History rather than logic. The UK, Ireland and most of Europe measure glucose in mmol/L, which counts molecules. The US, France and Japan use mg/dL, which measures weight per volume. Both describe the same thing, so converting between them is exact arithmetic.
How do I convert mmol/L to mg/dL?
Multiply by 18. More precisely 18.0182, which comes from the molar mass of glucose. To go the other way, divide by the same number. A reading of 5.5 mmol/L is about 99 mg/dL.
What is HbA1c and why does it have its own units?
HbA1c reflects your average blood sugar over roughly the previous three months, rather than a single moment. It is reported either in mmol/mol under the IFCC standard used in the UK, or as a percentage under the older DCCT standard still common in the US.
How do the HbA1c units relate?
Through a fixed linear formula: mmol/mol = (10.93 × percent) − 23.5. So 48 mmol/mol is 6.5%, and 53 mmol/mol is 7.0%. Those two pairs are the values you will most often see quoted together.
Is the conversion exact?
Yes, both are fixed mathematical relationships rather than estimates, so nothing is lost in translation. The only thing to watch is rounding — a value shown to one decimal place will convert to something slightly different from the same value shown to two.
Can this tell me whether my reading is normal?
No, and deliberately so. It converts units and nothing else. What a reading means depends on when it was taken, whether you had eaten, your treatment and your medical history — all of which need a doctor or diabetes team rather than a web page.