Glucose to A1C Calculator
Enter your average blood glucose to estimate your A1C percentage — in mg/dL or mmol/L.
mg/dL
Please enter a valid glucose value.
Input unit:
Estimated A1C
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%
eAG confirmation
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mg/dL
What this means
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Related guide
What Is A1C? A Complete Guide
Learn what A1C measures, how it's tested, and what your result means for diabetes management.
Read the guide →
How to Use This Calculator
1
Find your average glucose
Use the average from your glucose meter's memory, CGM app, or doctor's report. This should represent 2–3 months of readings for the most accurate A1C estimate.
2
Select your unit
Choose mg/dL (used in the US) or mmol/L (used in the UK, Canada, Australia). The calculator accepts both.
3
Read your estimated A1C
Your estimated A1C percentage appears with a clinical classification and plain-English explanation. Note: this is an estimate — only a lab test gives your official A1C.
The Formula
This calculator uses the inverse of the ADA ADAG formula:
A1C% = (eAG + 46.7) ÷ 28.7
Where eAG is in mg/dL. To convert mmol/L → mg/dL: multiply by 18.016
The ADAG (A1C-Derived Average Glucose) study, published by the ADA, established this bidirectional relationship between A1C and average glucose across thousands of participants over 3 months.
Average Glucose to A1C Reference Table
| Avg Glucose (mg/dL) | Avg Glucose (mmol/L) | Est. A1C % | Status |
|---|---|---|---|
| 97 | 5.4 | 5.0% | Normal |
| 111 | 6.2 | 5.5% | Normal |
| 117 | 6.5 | 5.7% | Upper Normal |
| 126 | 7.0 | 6.0% | Prediabetes Range |
| 140 | 7.8 | 6.5% | Diabetes Threshold |
| 154 | 8.6 | 7.0% | Above Target |
| 169 | 9.4 | 7.5% | Above Target |
| 183 | 10.2 | 8.0% | Above Target |
| 212 | 11.8 | 9.0% | High |
| 240 | 13.4 | 10.0% | Very High |
Source: NIDDK / NIH
Frequently Asked Questions
Can I estimate my A1C from my glucose meter average?
Yes, with limitations. If your glucose meter or CGM app shows an average glucose over the past 90 days, you can use this calculator to estimate your A1C. However, home glucose readings may not capture all time periods equally, especially overnight or post-meal spikes. The result is an estimate — your lab-measured A1C may differ by 0.5% or more.
What average glucose corresponds to a normal A1C?
A normal A1C below 5.7% corresponds to an average glucose below about 117 mg/dL (6.5 mmol/L). An A1C in the prediabetes range (5.7%–6.4%) corresponds to average glucose of roughly 117–140 mg/dL (6.5–7.8 mmol/L). An A1C at or above 6.5% — the diabetes diagnostic threshold — corresponds to an average glucose of 140 mg/dL (7.8 mmol/L) or higher.
What's the difference between this tool and the A1C Calculator on the homepage?
The main A1C Calculator converts A1C% → eAG (and back). This tool goes the other direction: you start with a known average glucose reading and estimate what your A1C might be. Both use the same ADA formula — just applied in opposite directions.
Does a CGM average equal eAG?
Not exactly. CGM reports a Time-in-Range average or a Glucose Management Indicator (GMI), while eAG is derived mathematically from A1C. In practice, they're similar but not identical — CGM captures real-time data continuously, while eAG is a mathematical estimate. If you use a CGM, your device's GMI may be a more direct comparison to A1C than this calculator's estimate.
How accurate is this glucose to A1C conversion?
The ADA ADAG formula has a correlation of 0.92 between A1C and eAG in clinical studies. In practice, individual variation means this estimate may be off by ±0.5% A1C. Factors like anemia, hemoglobin variants, or kidney disease can cause A1C to diverge from what glucose readings would predict. Always confirm with a lab test.