A1C Calculator

Q: What formula converts A1C to eAG?

The calculator uses the ADAG study regression endorsed by the ADA: eAG (mg/dL) = 28.7 x A1C - 46.7, with inverse A1C (%) = (eAG + 46.7) / 28.7. The relationship was published by Nathan et al. in Diabetes Care (2008) after measuring continuous and self-monitored glucose alongside A1C.

Q: How do I convert mg/dL to mmol/L for glucose?

Divide mg/dL by 18.0182 to get mmol/L; multiply mmol/L by 18.0182 to get mg/dL. The factor comes from glucose's molecular weight (180.156 g/mol) divided by 10. So 100 mg/dL equals 5.55 mmol/L, and 7 mmol/L equals 126.13 mg/dL.

Q: What A1C levels mean prediabetes and diabetes?

Per ADA: A1C below 5.7% is normal, 5.7% to 6.4% is prediabetes, and 6.5% or higher on two separate tests is the diagnostic cutoff for diabetes. The calculator labels each result and compares it against the ADA glycemic target (<7%) and the AACE target (<6.5%).

Q: Why does my real average glucose sometimes not match the eAG?

eAG is a population average that assumes a typical 120-day red blood cell lifespan and standard hemoglobin. Anemia, recent blood loss or transfusion, pregnancy, chronic kidney disease, and hemoglobin variants all shift the A1C-to-glucose relationship. CGM time-in-range and GMI may be more accurate in those cases.

Q: Is this calculator a substitute for medical advice?

No. This is an educational tool that performs the standard ADAG conversion and unit math. It does not diagnose diabetes, set your A1C target, or guide insulin dosing. Always review your A1C and glucose readings with your clinician.

Convert between A1C and estimated average glucose (eAG). Switch mg/dL and mmol/L. ADA diagnostic thresholds and ADA/AACE targets included.

A1C, eAG, and glucose

What do you want to do?

A1C (%)

Enter the percent value from your lab report. Typical reporting range is 3% to 20%.

Estimated average glucose

7% A1C

154.2 mg/dL|8.56 mmol/L

Diabetes range (ADA: A1C 6.5% or higher)

Above ADA (<7%) target; many clinicians individualize to <8%

Medical disclaimer

This calculator is for educational use only and is not a diagnosis or treatment plan. The A1C to eAG relationship (ADAG study, 28.7 x A1C - 46.7) is an average across many people; your real average glucose depends on red blood cell lifespan, hemoglobin variants, anemia, pregnancy, and other factors that can shift the mapping. Always discuss your A1C and glucose results with your clinician before changing medication, diet, or insulin doses.

Frequently Asked Questions about the A1C Calculator

What formula converts A1C to eAG?

The calculator uses the ADAG study regression endorsed by the ADA: eAG (mg/dL) = 28.7 x A1C - 46.7, with inverse A1C (%) = (eAG + 46.7) / 28.7. The relationship was published by Nathan et al. in Diabetes Care (2008) after measuring continuous and self-monitored glucose alongside A1C.

How do I convert mg/dL to mmol/L for glucose?

Divide mg/dL by 18.0182 to get mmol/L; multiply mmol/L by 18.0182 to get mg/dL. The factor comes from glucose's molecular weight (180.156 g/mol) divided by 10. So 100 mg/dL equals 5.55 mmol/L, and 7 mmol/L equals 126.13 mg/dL.

What A1C levels mean prediabetes and diabetes?

Per ADA: A1C below 5.7% is normal, 5.7% to 6.4% is prediabetes, and 6.5% or higher on two separate tests is the diagnostic cutoff for diabetes. The calculator labels each result and compares it against the ADA glycemic target (<7%) and the AACE target (<6.5%).

Why does my real average glucose sometimes not match the eAG?

eAG is a population average that assumes a typical 120-day red blood cell lifespan and standard hemoglobin. Anemia, recent blood loss or transfusion, pregnancy, chronic kidney disease, and hemoglobin variants all shift the A1C-to-glucose relationship. CGM time-in-range and GMI may be more accurate in those cases.

Is this calculator a substitute for medical advice?

No. This is an educational tool that performs the standard ADAG conversion and unit math. It does not diagnose diabetes, set your A1C target, or guide insulin dosing. Always review your A1C and glucose readings with your clinician.

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