A1C Calculator
Convert an A1C percentage to estimated average glucose (eAG) in mg/dL and mmol/L, or go the other way, and see where the number falls on the ADA scale.
From your lab report, e.g. 6.4.
- A1C (NGSP)
- 7%
- A1C (IFCC)
- 53 mmol/mol
- eAG in mg/dL
- 154 mg/dL
- eAG in mmol/L
- 8.6 mmol/L
- ADA category
- Diabetes (6.5% and above)
| A1C | eAG mg/dL | eAG mmol/L | Category |
|---|---|---|---|
| 5% | 97 | 5.4 | Normal |
| 5.5% | 111 | 6.2 | Normal |
| 6% | 126 | 7 | Prediabetes |
| 6.5% | 140 | 7.8 | Diabetes |
| 7% | 154 | 8.6 | Diabetes |
| 7.5% | 169 | 9.4 | Diabetes |
| 8% | 183 | 10.2 | Diabetes |
| 8.5% | 197 | 10.9 | Diabetes |
| 9% | 212 | 11.7 | Diabetes |
| 9.5% | 226 | 12.5 | Diabetes |
| 10% | 240 | 13.3 | Diabetes |
| 10.5% | 255 | 14.1 | Diabetes |
| 11% | 269 | 14.9 | Diabetes |
| 11.5% | 283 | 15.7 | Diabetes |
| 12% | 298 | 16.5 | Diabetes |
How this was calculated
- eAG = 28.7 × 7 − 46.7 = 154.2 mg/dL.
- In mmol/L: 154.2 ÷ 18.016 = 8.6 mmol/L.
- IFCC units: (7 − 2.15) × 10.929 = 53 mmol/mol.
The eAG formula describes the average relationship in a study population; an individual's A1C can sit above or below it. A diagnosis of prediabetes or diabetes requires a laboratory test ordered and interpreted by a clinician. This is general information, not medical advice.
How this A1C calculator works
Hemoglobin A1C measures the share of your red blood cells' hemoglobin that has glucose attached. Because red cells live about three months, the percentage reflects your average blood sugar over roughly the last 8 to 12 weeks, weighted toward the most recent month. Doctors report it as a percentage, but most people think about blood sugar in the units their meter shows, so this A1C calculator converts between the two using the formula the American Diabetes Association adopted from the 2008 ADAG study: eAG (mg/dL) = 28.7 × A1C − 46.7. "eAG" stands for estimated average glucose. To get mmol/L, the unit used outside the US, divide mg/dL by 18.016. Going the other way, A1C = (eAG + 46.7) ÷ 28.7.
The calculator also shows the result in IFCC units (mmol/mol), which labs in the UK, Europe and Australia use, and places the A1C on the ADA scale: below 5.7% is normal, 5.7% to 6.4% is the prediabetes range and 6.5% or above is the diabetes range. Those cut-offs are for context. A diagnosis is made from a laboratory-run A1C, usually confirmed with a second test, never from a calculator.
Worked example
Your lab report says A1C 7.0%. Multiply by 28.7 to get 200.9, subtract 46.7 and the estimated average glucose is 154 mg/dL, or 154.2 ÷ 18.016 = 8.6 mmol/L. In IFCC units that is (7.0 − 2.15) × 10.929 = 53 mmol/mol. The reverse works the same way: if your meter's 90-day average is 126 mg/dL, then (126 + 46.7) ÷ 28.7 = 6.0%, right at the top of the prediabetes range. Each 1-point change in A1C corresponds to about 29 mg/dL (1.6 mmol/L) of average glucose, so dropping from 8% to 7% means an average roughly 29 mg/dL lower across the whole day, every day.
Common mistakes
- Comparing eAG to a fasting reading. eAG is a 24-hour average that includes the rise after every meal. A fasting glucose of 110 mg/dL and an eAG of 154 mg/dL can easily belong to the same person.
- Expecting your meter average to match exactly. Meter averages only include the moments you test, usually before meals, so they run lower than eAG. A continuous glucose monitor's 90-day average is a fairer comparison.
- Mixing up units. 7.0 is an A1C percentage; 7.0 mmol/L is a glucose reading of 126 mg/dL. The toggle sets which unit the glucose box is in.
When the conversion is misleading
The ADAG formula is a best-fit line through hundreds of people, and individuals scatter around it: for an A1C of 7.0%, 95% of participants had true averages between about 123 and 185 mg/dL. Anything that changes red-cell lifespan moves A1C independently of glucose. Iron-deficiency anemia, recent blood loss or transfusion, pregnancy, kidney disease, hemoglobin variants such as sickle-cell trait, and high-dose vitamin C or E can all push the number up or down. If your A1C and your meter disagree by more than the formula predicts, that is a conversation for your clinician, who may use fructosamine or CGM data instead.
Frequently asked questions
›How do you convert A1C to average glucose?
eAG (mg/dL) = 28.7 × A1C − 46.7, the ADAG formula used by the American Diabetes Association. An A1C of 7.0% equals 28.7 × 7 − 46.7 = 154 mg/dL, or 8.6 mmol/L (divide mg/dL by 18.016).
›How do you convert average glucose to A1C?
A1C = (eAG in mg/dL + 46.7) ÷ 28.7. An average of 126 mg/dL converts to (126 + 46.7) ÷ 28.7 = 6.0%. Convert mmol/L to mg/dL first by multiplying by 18.016.
›What is a normal A1C level?
Below 5.7% is normal, 5.7% to 6.4% is the prediabetes range and 6.5% or higher is in the diabetes range, according to the American Diabetes Association. Diagnosis requires a lab test, usually repeated.
›What A1C is equal to 154 mg/dL?
7.0%. The ADA often uses this pair as its reference example; each 1-point change in A1C is about 29 mg/dL (1.6 mmol/L) of average glucose.
›Why doesn't my meter average match my A1C?
Meter averages only include the moments you test, usually before meals, while eAG covers all 24 hours including post-meal rises. Conditions that change red-cell lifespan, such as anemia, pregnancy or kidney disease, also shift A1C independently of glucose.