HbA1c to estimated average glucose calculator
Understand the relationship between HbA1c and average glucose using the ADAG regression equation.
Formula & units
eAG (mg/dL) = 28.7 × HbA1c (%) − 46.7
The reverse estimate is HbA1c (%) = [average glucose (mg/dL) + 46.7] ÷ 28.7. This is a population estimate; this tool accepts the educational A1c range 4–15%.
Worked example
HbA1c 7% corresponds to an estimated average glucose of 154.2 mg/dL, or 8.57 mmol/L.
What the result can tell you
A single fasting or post-meal reading cannot substitute for average glucose. Estimated A1c is not a laboratory A1c result or CGM-derived GMI. Individual results may differ.
Read the interpretation guide →
Sources for this method
Questions about HbA1c ↔ eAG
What average glucose corresponds to HbA1c of 7%?
The ADAG equation gives approximately 154 mg/dL, or 8.6 mmol/L. This is a population-based estimate rather than an exact prediction for every person.
Source: Nathan et al. · ADAG study, 2008 (opens in a new tab) · Related calculator → · Link to answer
Do I need to fast for an HbA1c test?
An HbA1c test itself does not require fasting. If other blood tests are ordered at the same visit, follow the preparation instructions for those tests.
Source: NIDDK · The A1C test and diabetes (opens in a new tab) · Related calculator → · Link to answer
Can I estimate HbA1c from one fasting glucose result?
No reliable individual estimate follows from a single fasting reading. The reverse ADAG equation expects representative average glucose over time.
Source: Nathan et al. · ADAG study, 2008 (opens in a new tab) · Related calculator → · Link to answer
Why can HbA1c and average glucose disagree?
A1c reflects glucose exposure over time, while individual readings capture moments. Changes in red blood cells, some hemoglobin variants, and other conditions can also affect A1c accuracy.
Source: NIDDK · The A1C test and diabetes (opens in a new tab) · Related calculator → · Link to answer
Does HbA1c show today’s glucose level?
HbA1c reflects glucose exposure over approximately three months. It cannot show the timing or size of a particular glucose spike.
Source: NIDDK · The A1C test and diabetes (opens in a new tab) · Related calculator → · Link to answer
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