Convert 42 mmol/mol to HbA1c percentage
(0.09148 × 42) + 2.152 = 5.99
Displayed result: 6.0%
Blood sugar calculator
HbA1c converter: mmol/mol, % and estimated average glucose
Convert an HbA1c result between the UK IFCC unit (mmol/mol) and NGSP percentage, with an optional estimated average glucose shown in mmol/L and mg/dL.
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HbA1c converter
Educational conversion only. Laboratory ranges vary, and unexpected results should be discussed with a qualified clinician.
Three simple steps
How to use this calculator
Use the wording and unit from your original laboratory report. Keep that report available when reviewing the converted value.
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1
Find the HbA1c line on your report
Use the laboratory HbA1c value, not a single finger-prick glucose reading or continuous-glucose-monitor average.
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2
Select the unit exactly as printed
UK reports usually use mmol/mol. International reports may show HbA1c as a percentage using NGSP/DCCT units.
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3
Read the equivalent values
The calculator shows both HbA1c units and an estimated average glucose. Keep the original laboratory value when discussing the result with a clinician.
How it works
About this calculation
HbA1c reflects how much haemoglobin has glucose attached to it. UK laboratories generally report mmol/mol, while some international reports and research use a percentage. Estimated average glucose is a mathematical estimate, not a replacement for glucose-monitor readings.
Worked answers
Conversion examples and common values
These examples show the arithmetic and the rounding used by the calculator. They are not reference ranges or personal targets.
Convert 6.5% to mmol/mol
(6.5 − 2.152) ÷ 0.09148 = 47.53
Displayed result: 48 mmol/molEstimate average glucose from 7.0%
(28.7 × 7.0) − 46.7 = 154.2
Displayed estimate: 154 mg/dL| IFCC (mmol/mol) | NGSP/DCCT (%) | Estimated average glucose (mg/dL) |
|---|---|---|
| 31 | 5.0 | 97 |
| 42 | 6.0 | 126 |
| 48 | 6.5 | 140 |
| 53 | 7.0 | 154 |
| 64 | 8.0 | 183 |
| 75 | 9.0 | 212 |
Why HbA1c has two reporting systems
IFCC reporting expresses glycated haemoglobin as millimoles of HbA1c per mole of haemoglobin. NGSP/DCCT reporting expresses the same measurement as a percentage. Converting the unit does not change the blood sample or the result itself.
Estimated average glucose translates HbA1c into a glucose-style unit. It is derived from a population equation, so it may not match an individual person’s meter or continuous-monitor average exactly.
Important context
Limitations
HbA1c and estimated average glucose may not align for every person. Red-cell lifespan, anaemia, haemoglobin variants, pregnancy, kidney disease and recent blood loss or transfusion can affect HbA1c. Use the result from your own laboratory report and discuss unexpected values with a qualified clinician.
Questions about this tool
Frequently asked questions
These answers explain the calculation and its limitations. They do not interpret an individual laboratory result.
What is an HbA1c of 42 mmol/mol as a percentage?
Using the IFCC-to-NGSP master equation, 42 mmol/mol converts to approximately 6.0%. The conversion changes the reporting unit, not the underlying result.
Is estimated average glucose the same as my glucose meter average?
No. Estimated average glucose is calculated from HbA1c using a population equation. A meter or continuous monitor measures glucose at particular times, so the averages may differ.
Can I enter a GMI value from a continuous glucose monitor?
This tool is intended for a laboratory HbA1c result. Glucose Management Indicator (GMI) is calculated from continuous-monitor data and should not be treated as a measured HbA1c.
Why does the UK use mmol/mol for HbA1c?
UK laboratories generally follow the IFCC reporting system, while percentage reporting remains common in the United States and in some international material. Both describe HbA1c using different scales.
Can health conditions affect how HbA1c relates to average glucose?
Yes. Conditions that affect red blood cells or haemoglobin can alter HbA1c independently of average glucose. Pregnancy, anaemia, kidney disease, recent blood loss and transfusion are examples requiring clinical context.
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