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A1C Calculator
A1C ↔ eAG, GMI from CGM, IFCC mmol/mol and the ADA category — a screening estimate. Accurate, instant and free — for United States.
What these mean:
What these mean:
An A1C of 7% ≈ 154 mg/dL (8.6 mmol/L) estimated average glucose, 53 mmol/mol IFCC. Category: diabetes.
Rates as of 2026eAG (mg/dL)
154 mg/dL
eAG (mmol/L)
8.6 mmol/L
A1C (%)
7%
IFCC (mmol/mol)
53 mmol/mol
ADA category: diabetes — In the ADA diabetes range (≥ 6.5%)
eAG is not the same as GMI
Screening estimate, not a diagnosis
How we calculate this
Reviewed by Reckonist Editorial · Last reviewed July 2026. Figures follow the methods and sources set out in our editorial standards.
These conversions use the NGSP/ADAG eAG equation, Bergenstal 2018 GMI, and ADA 2026 thresholds. General health information, not medical advice — consult a clinician.
ADAG eAG · GMI Bergenstal 2018 · ADA Standards of Care 2026
Tracking kidney function too? See the eGFR Calculator.
How A1C, eAG and GMI relate
A1C (HbA1c) reflects your average glucose over roughly the past 2–3 months. This tool converts an A1C to estimated average glucose (eAG) with the ADAG equation, back-solves an A1C from an average glucose, computes GMI from a CGM mean glucose, and shows the IFCC mmol/mol equivalent plus the ADA category.
A1C ↔ eAG (ADAG)
lab A1C → average glucose
eAG(mg/dL) = 28.7 × A1C − 46.7 ; mmol/L = ÷ 18.0156
Reverse: A1C = (eAG + 46.7) / 28.7. IFCC mmol/mol = (A1C − 2.15) × 10.929.
GMI (Bergenstal 2018)
CGM mean glucose → estimate
GMI% = 3.31 + 0.02392 × mean glucose(mg/dL)
A CGM-derived estimate of A1C — not a lab A1C, and it commonly differs.
- 1A1C → eAG: 28.7 × 7 − 46.7 = 154 mg/dL; ÷ 18.0156 = 8.6 mmol/L.
- 2GMI is different: A CGM mean glucose of 150 mg/dL gives GMI = 3.31 + 0.02392 × 150 ≈ 6.9% — below the 7% lab A1C above, showing eAG ≠ GMI.
eAG is not GMI — and A1C isn't always reliable
The single most common error — including in AI answers — is treating a CGM's GMI as a lab A1C. They come from different equations and different sources, and they commonly disagree.
eAG comes from a lab A1C; GMI comes from a CGM
A1C is a screening estimate, not a diagnosis
ADA categories & the units you'll see
ADA Standards of Care screening categories: below 5.7% normal, 5.7–6.4% prediabetes, 6.5% or higher diabetes. Glucose is reported in mg/dL (US) or mmol/L (international, mg/dL ÷ 18.0156), and A1C itself in NGSP % or IFCC mmol/mol. Mislabelling units on a medical page is dangerous — this tool keeps them in sync and labels every value.
Frequently asked questions
A1C converts to estimated average glucose using the ADAG equation: eAG (mg/dL) = 28.7 × A1C − 46.7. Divide that by 18.0156 for mmol/L. For example, an A1C of 7% is about 154 mg/dL (8.6 mmol/L). The reverse is A1C = (eAG + 46.7) / 28.7, so an average glucose of 154 mg/dL maps back to roughly 7.0%. These are estimates — the ADAG study reported a strong but not perfect correlation (r² = 0.84).
No. GMI (Glucose Management Indicator) is calculated from your CGM mean glucose using GMI% = 3.31 + 0.02392 × mean glucose (mg/dL), a different equation introduced by Bergenstal in 2018. It estimates A1C but commonly differs from a lab A1C — validation studies found about 1 in 5 people differ by 0.5 percentage points or more. GMI answers "what has my average been on the CGM"; a lab A1C measures glycated hemoglobin directly. Never treat a CGM-derived GMI as your official A1C.
Using the ADA Standards of Care screening categories: an A1C below 5.7% is normal, 5.7% to 6.4% is prediabetes, and 6.5% or higher is in the diabetes range. These are screening thresholds, not a diagnosis on their own — diagnosis usually requires confirmation and clinical context, so discuss any result with a clinician.
Most of the world outside the US reports A1C in IFCC units (mmol/mol) rather than NGSP percent. The conversion is mmol/mol = (A1C% − 2.15) × 10.929, so a 7% NGSP A1C equals about 53 mmol/mol. Our calculator shows both so you can read a lab report in either system.
A1C depends on red blood cell lifespan, so it can be misleading in anemia, hemoglobinopathies (such as HbS, HbC or HbE traits), recent blood transfusion, pregnancy (especially the 2nd and 3rd trimesters), advanced chronic kidney disease or erythropoietin use, and any condition with high red-cell turnover. In those situations A1C may not reflect true average glucose — a clinician may rely on fructosamine, CGM data or direct glucose testing instead.
Yes — it is completely free with no sign-up, and every calculation runs entirely in your browser. Nothing you enter is sent to a server or stored. It is general health information for education, not medical advice.
Method, standards & references
Methodology: eAG uses the ADAG equation (28.7×A1C − 46.7 mg/dL; ÷18.0156 for mmol/L); the reverse is (eAG + 46.7)/28.7. GMI uses Bergenstal 2018 (3.31 + 0.02392 × CGM mean glucose) and is distinct from a lab A1C. IFCC mmol/mol = (A1C − 2.15) × 10.929. ADA categories: normal <5.7%, prediabetes 5.7–6.4%, diabetes ≥6.5%. Constants are held in versioned config (ADA Standards of Care 2026; NGSP/ADAG; Bergenstal 2018 (GMI)); all calculations run client-side and nothing is stored. Reference data as of 2026. Screening estimate, not a diagnosis.
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How we calculate this
Reviewed by Reckonist Editorial · Last reviewed July 2026. Figures follow the methods and sources set out in our editorial standards.
These conversions use the NGSP/ADAG eAG equation, Bergenstal 2018 GMI, and ADA 2026 thresholds. eAG is derived from a lab A1C; GMI is CGM-derived and commonly differs — it is not your A1C. This is general health information for education, not medical advice, and not a diagnosis. A1C is unreliable in several conditions (anemia, hemoglobinopathies, pregnancy, recent transfusion, CKD) — always confirm with a clinician.
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