Enter the HbA1c value in mmol/mol or the HbA1c percentage into the calculator to determine the missing variable.
Medical note: This calculator is for educational use only and is not medical advice. Do not use it to diagnose diabetes/prediabetes or to change medications, diet, or treatment without a licensed clinician. HbA1c results can be misleading in situations such as pregnancy, anemia/iron deficiency, hemoglobin variants, recent blood loss or transfusion, and some kidney or liver conditions.
References and standards
- For the HbA1c IFCC↔NGSP conversion (“master equation”), check the NGSP and IFCC official documentation.
- For patient-friendly guidance on HbA1c testing and interpretation, check major clinical organizations (e.g., ADA) and public health agencies (e.g., CDC).
Last reviewed: January 2026
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HbA1c To Percentage Formula
The following formulas are used to convert HbA1c values between mmol/mol (IFCC) and percentage (NGSP/DCCT).
\begin{aligned}
HbA1c_{\%} &= 0.09148 \times HbA1c_{mmol/mol} + 2.152 \\
HbA1c_{mmol/mol} &= \frac{HbA1c_{\%} - 2.152}{0.09148}
\end{aligned}Variables:
- HbA1cmmol/mol is the HbA1c value in mmol/mol (IFCC units)
- HbA1c% is the HbA1c value in percent (NGSP/DCCT units)
To convert HbA1c values, use the formulas above. For example, to convert from mmol/mol to percentage, multiply the mmol/mol value by 0.09148 and add 2.152. To convert from percentage to mmol/mol, subtract 2.152 from the percentage value and then divide by 0.09148.
| HbA1c (mmol/mol) | HbA1c (%) |
|---|---|
| 10 | 3.067 |
| 20 | 3.982 |
| 25 | 4.439 |
| 28 | 4.713 |
| 30 | 4.896 |
| 32 | 5.079 |
| 35 | 5.354 |
| 38 | 5.628 |
| 40 | 5.811 |
| 42 | 5.994 |
| 45 | 6.269 |
| 48 | 6.543 |
| 50 | 6.726 |
| 53 | 7.000 |
| 55 | 7.183 |
| 58 | 7.458 |
| 60 | 7.641 |
| 65 | 8.098 |
| 70 | 8.556 |
| 75 | 9.013 |
| Formula used: HbA1c (%) = 0.09148 × HbA1c (mmol/mol) + 2.152. Reverse: HbA1c (mmol/mol) = (HbA1c (%) − 2.152) / 0.09148. | |
Note: This table shows a mathematical unit conversion. Typical clinical ranges and targets vary by individual and situation; unusually low or high HbA1c values should be interpreted with a clinician and may reflect medical conditions or assay limitations.
What is HbA1c?
HbA1c, also known as glycated hemoglobin, is a form of hemoglobin that is chemically linked to a sugar. It is used primarily to estimate average blood glucose over the past ~2–3 months. HbA1c is commonly used to help diagnose diabetes and prediabetes and to monitor long-term glucose control. Type 1 diabetes diagnosis often also relies on blood glucose testing and clinical evaluation, especially when symptoms develop quickly.
How to Convert HbA1c?
The following steps outline how to convert HbA1c between mmol/mol and percentage.
- First, determine the HbA1c value you have (either mmol/mol or percentage).
- Next, choose the correct conversion formula for the direction you need.
- Insert the known value into the formula and solve for the unknown value.
- Finally, check your answer with the calculator above.
Example Problem :
Use the following variables as an example problem to test your knowledge.
HbA1c (mmol/mol) = 42
HbA1c Percentage (%) = 6.0
