mg/dL to A1C Calculator

By: Patrick Myers Patrick Myers is the CEO and Founder of Calculator Academy. He has over eight years of experience developing online calculators and holds a B.S. in Mechanical Engineering. His work focuses on formula implementation, calculator accuracy, unit conversions, and creating practical tools that are easy to use.

Last Updated: July 16, 2026

Convert average glucose in mg/dL or mmol/L to estimated A1C, or convert A1C back to eAG, with NGSP and IFCC units plus interpretation guidance.

Required: an average glucose value and its unit.

Enter a multi-day or longer average, not one fasting, random, or post-meal reading.

Uses the ADAG population equation eAG = 28.7 × A1C − 46.7. A1C reflects average glucose over roughly the prior 2–3 months, but recent weeks contribute more. Estimates may not match a laboratory A1C and can be unreliable with altered red-blood-cell lifespan, anemia, recent transfusion, pregnancy, kidney disease, or hemoglobin variants. Do not use this estimate to diagnose diabetes or change treatment without a qualified clinician.

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Formula

The calculator uses the ADAG (A1C-Derived Average Glucose) linear regression from Nathan et al., 2008.

mg/dL → A1C: A1C = (eAG + 46.7) / 28.7
A1C → mg/dL: eAG = 28.7 × A1C − 46.7
where eAG = estimated average glucose (mg/dL), A1C in %.

Unit conversions: mg/dL = mmol/L × 18.0182
IFCC (mmol/mol) = (A1C% − 2.15) × 10.929

Interpretation

The A1C reflects your average blood glucose over the prior 2–3 months, weighted toward the most recent weeks. The eAG tells you what daily meter reading, on average, would correspond to a given A1C. Use the thresholds below (American Diabetes Association):

  • Normal: A1C below 5.7% (eAG below ~117 mg/dL)
  • Prediabetes: A1C 5.7%–6.4% (eAG ~117–137 mg/dL)
  • Diabetes: A1C 6.5% or higher (eAG ~140 mg/dL or higher)
  • Typical treatment target for adults with diabetes: A1C below 7.0% (eAG ~154 mg/dL)

Remember this is an estimate. Your actual A1C can differ from the predicted value by roughly ±0.5% because hemoglobin turnover, anemia, kidney disease, pregnancy, and certain hemoglobin variants all change the relationship between glucose and glycated hemoglobin.

Conversion Reference Table

A1C (%)eAG (mg/dL)eAG (mmol/L)IFCC (mmol/mol)
5.0975.431
5.71176.539
6.01267.042
6.51407.848
7.01548.653
7.51699.458
8.018310.164
9.021211.875
10.024013.386
12.029816.5108

FAQ

Should I enter a single fasting glucose or an average?
Enter an average. A1C correlates with mean glucose across all times of day over months, not with one fasting reading. A CGM time-in-range average or a fingerstick average from at least two weeks of testing gives the most realistic estimate.

Why doesn’t my estimated A1C match my lab A1C?
The formula is a population average. Individual “glycators” process glucose into HbA1c at slightly different rates, and conditions that shorten red blood cell lifespan (iron deficiency, hemolysis, recent transfusion, sickle trait, pregnancy) can shift your real A1C away from the predicted value by 0.3–1.0% or more.

What’s the difference between A1C (%) and IFCC (mmol/mol)?
They measure the same thing on different scales. NGSP percent is standard in the US; IFCC mmol/mol is standard in most of Europe and Australia. The calculator shows both.

Can I use this if I’m not diabetic?
Yes, the formula works across the full glucose range, but estimates below ~5.0% or above ~12% are extrapolations outside the original study data and lose accuracy at the extremes.

mg/dL to A1C Calculator