An A1C result reports a percentage, but daily glucose readings come in milligrams per deciliter or millimoles per liter. This calculator bridges the two using the formula from the A1C-Derived Average Glucose (ADAG) study, so you can see what your A1C means in meter units, or estimate the A1C that a given average would produce.
How to use the A1C calculator
- Choose the direction: A1C → average glucose or average glucose → A1C.
- Enter your A1C percentage, or your average glucose in mg/dL or mmol/L.
- Read the estimated average glucose (eAG) in both units, the A1C in IFCC units (mmol/mol) and where the value falls against the American Diabetes Association ranges.
- Use the table to look up any A1C from 5% to 14%.
A1C to eAG formula
From the ADAG study (Nathan and colleagues, Diabetes Care, 2008):
Worked example
A lab report shows an A1C of 8.0%:
eAG = 28.7 × 8.0 − 46.7 = 229.6 − 46.7 = 183 mg/dL
In mmol/L: 182.9 ÷ 18.016 = 10.2 mmol/L
IFCC: (8.0 − 2.15) × 10.929 = 64 mmol/mol. This is in the diabetes range and above the common goal of under 7% for many adults.
Going the other way, an average of 7.8 mmol/L (140.5 mg/dL) corresponds to an A1C of (140.5 + 46.7) ÷ 28.7 ≈ 6.5%.
A1C and average glucose chart
| A1C | eAG (mg/dL) | eAG (mmol/L) | IFCC (mmol/mol) |
|---|---|---|---|
| 5.0% | 97 | 5.4 | 31 |
| 5.7% | 117 | 6.5 | 39 |
| 6.0% | 126 | 7.0 | 42 |
| 6.5% | 140 | 7.8 | 48 |
| 7.0% | 154 | 8.6 | 53 |
| 8.0% | 183 | 10.2 | 64 |
| 9.0% | 212 | 11.7 | 75 |
| 10.0% | 240 | 13.3 | 86 |
| 12.0% | 298 | 16.5 | 108 |
Each 1-point change in A1C corresponds to about 29 mg/dL (1.6 mmol/L) of average glucose.
ADA categories and goals
| A1C | Category |
|---|---|
| Below 5.7% | Normal range |
| 5.7% to 6.4% | Prediabetes |
| 6.5% or higher | Diabetes range (confirmed by repeat testing) |
For many nonpregnant adults with diabetes, the ADA suggests an A1C goal below 7%. Goals are individualized: tighter targets may suit some younger, healthy adults, while looser targets are often safer for older adults or people prone to low blood sugar.
When A1C can mislead
The ADAG formula describes the average relationship in its study group, and individuals scatter around it. Two people with the same A1C can have average glucose levels that differ noticeably. A1C can also be distorted by conditions that change red blood cell lifespan, such as iron-deficiency anemia, hemolysis, recent transfusion, advanced kidney disease and pregnancy, and by some inherited hemoglobin variants. Continuous glucose monitoring reports a related measure, the glucose management indicator (GMI), which can be compared with lab A1C.
Lifestyle factors that improve A1C over time include weight loss when needed, regular activity and a balanced diet. The weight loss calculator, BMI calculator and waist-to-hip ratio calculator can help track related measures.
Informational only — not medical advice. Diabetes is diagnosed and managed by healthcare professionals using laboratory tests; do not change medication based on this calculator.
Frequently asked questions
What does A1C measure?
A1C is the percentage of hemoglobin in red blood cells that has glucose attached. Because red cells live about three months, it reflects average blood sugar over roughly the previous two to three months, weighted toward the most recent weeks.
What A1C is normal?
The American Diabetes Association classifies an A1C below 5.7% as normal, 5.7–6.4% as prediabetes and 6.5% or higher as the diabetes range. A diagnosis requires a lab test and, usually, a confirming second test.
What is eAG?
Estimated average glucose translates A1C into the units of a glucose meter. It comes from the A1C-Derived Average Glucose (ADAG) study, which compared A1C with continuous glucose monitoring in 507 adults and found eAG = 28.7 × A1C − 46.7 in mg/dL.
Why does my meter average differ from my eAG?
Fingerstick averages over-represent the times you test, often before meals. A1C also varies with red blood cell lifespan, so anemia, recent blood loss, kidney disease and some hemoglobin variants can make it read higher or lower than your true average.
What is the IFCC unit?
Many countries report A1C in millimoles per mole (mmol/mol) as standardized by the International Federation of Clinical Chemistry. 7% NGSP equals 53 mmol/mol, and 6.5% equals 48 mmol/mol.