A1c to Average Glucose Calculator
Convert an HbA1c result into the estimated average glucose it represents, in mmol/L and mg/dL, and into the IFCC mmol/mol units, using the ADAG study equation.
What your HbA1c means as an everyday blood-sugar number.
How the a1c to average glucose calculator works
HbA1c measures the share of haemoglobin with glucose attached and reflects average blood glucose over the previous two to three months. The ADAG study (2008) fitted the relationship eAG (mg/dL) = 28.7 × A1c − 46.7, which is what the calculator uses; dividing by 18 gives mmol/L. The IFCC unit, mmol/mol, is a linear conversion: (A1c % − 2.15) × 10.929.
The verdict names the 6.5% (48 mmol/mol) level that diagnostic guidelines use internationally for diabetes. It does not diagnose anything — a doctor interprets results with the whole picture.
Formula: eAG (mg/dL) = 28.7 × A1c − 46.7 · mmol/L = mg/dL ÷ 18.0182 · IFCC = (A1c − 2.15) × 10.929
Worked examples
| Inputs | Estimated average glucose | Note |
|---|---|---|
| HbA1c 5.8% | 6.6 | eAG 119.8 mg/dL = 6.6 mmol/L |
| HbA1c 6.5% | 7.8 | the diagnostic level: 140 mg/dL, 48 mmol/mol |
| HbA1c 8.0% | 10.2 | 183 mg/dL = 10.2 mmol/L |
FAQFrequently asked questions
What is estimated average glucose?
A translation of HbA1c into the units of a glucose meter, so the two can be compared. It comes from the ADAG study, which matched A1c against continuous glucose monitoring in 507 people.
Why do labs report mmol/mol?
The IFCC standardised unit. 6.5% is 48 mmol/mol; 7% is 53. Many countries report both.
Is 6.5% the same threshold everywhere?
The 6.5% diagnostic level for diabetes is used by WHO, the ADA and national bodies. The "at-risk" or prediabetes band below it is defined differently by different guidelines, so this calculator does not label it.
Can I convert an average meter reading back to A1c?
Yes — rearrange the same equation: A1c = (mg/dL + 46.7) ÷ 28.7. A 3-month meter average of 150 mg/dL corresponds to about 6.9%.
Where these figures come from
- Mifflin MD et al., "A new predictive equation for resting energy expenditure in healthy individuals", Am J Clin Nutr 1990 — the BMR equation used here
- World Health Organization — Waist circumference and waist–hip ratio (2008 expert consultation) — waist-to-hip cut-offs
- Tanaka H, Monahan KD, Seals DR, "Age-predicted maximal heart rate revisited", J Am Coll Cardiol 2001 — 208 − 0.7 × age
- Nathan DM et al., "Translating the A1C assay into estimated average glucose values" (ADAG), Diabetes Care 2008 — eAG = 28.7 × A1c − 46.7
- Mosteller RD, "Simplified calculation of body-surface area", N Engl J Med 1987 — BSA = √(height × weight / 3600)
- NHS — national health guidance
Last checked: September 2026. The equations are fixed by their published papers and do not change with tax years or regulations; the thresholds quoted in verdicts name the body that set them.