A1C to Blood Sugar Calculator
Average glucose in mg/dL and mmol/L from A1C percent.
What it does
Hemoglobin A1C records what fraction of red blood cells carries sugar, which averages glucose over their two to three month life. The ADAG study fitted lab averages to A1C values with the line 28.7 times A1C minus 46.7, now standard worldwide.
The tool above takes the A1C percent. It returns estimated average glucose in mg/dL and mmol/L with the diagnostic band.
Averages hide swings that matter. Two people sharing 7% can differ wildly in spikes and lows, which continuous monitors reveal and A1C averages away.
Anemia, kidney disease, and hemoglobin variants bend A1C away from true averages. Fructosamine and sensor data arbitrate when labs and meters disagree.
How to use
- Enter the lab A1C percent, not a meter average.
- Read mg/dL first, mmol/L beside it.
- Check the band against diagnostic cutoffs.
- Set personal targets with the clinician, not the chart.
Formula
- 28.7
- Slope from the ADAG regression of glucose on A1C.
- 46.7
- Intercept aligning the line to lab data.
- 18.0156
- mg/dL per mmol/L for glucose.
Individual scatter runs about plus or minus 15 mg/dL around the line. The estimate centers populations better than persons.
Worked example
Example: A1C 7%
Lab result 7.0%.
- Glucose: 28.7 x 7 - 46.7 = 200.9 - 46.7 = 154 mg/dL.
- Metric: 154.2 / 18.0156 = 8.6 mmol/L.
- Band: 6.5 and above reads diabetes range.
- Target: many adults aim under 7% with their clinician.
Reference table
| A1C | mg/dL | mmol/L |
|---|---|---|
| 5% | 97 | 5.4 |
| 6% | 126 | 7.0 |
| 7% | 154 | 8.6 |
| 8% | 183 | 10.2 |
| 9% | 212 | 11.7 |
| 10% | 240 | 13.3 |
Limits
- Estimate with individual scatter near 15 mg/dL.
- Anemia and variants distort A1C readings.
- Pregnancy uses different targets and tests.
- Meters and sensors read instants, not averages.
Common mistakes
- Treating estimate as exact daily average.
- Chasing A1C with lows that average out.
- Comparing finger sticks directly to A1C.
- Ignoring conditions that skew hemoglobin.
- Setting targets without clinician context.
Try it yourself
Quick checks. Answers sit tucked under each question.
A1C 6%?
28.7 x 6 - 46.7 = 125.5, shown as 126 mg/dL.
154 mg/dL in mmol/L?
154.2 / 18.0156 = 8.6 mmol/L.
Questions
What is a good A1C?
Under 5.7 normal. Many treated adults target under 7% individually set.
What does 7% mean daily?
About 154 mg/dL average over months, hiding daily swings.
How often is A1C tested?
Two to four times yearly depending on control and therapy changes.
Can A1C be wrong?
Yes with anemia, kidney disease, or hemoglobin variants. Other tests arbitrate.
Does fasting affect A1C?
No. It averages months regardless of the test day meal.
How do I lower A1C?
Medication adherence, meals, movement, sleep, and clinician follow up together.