Unit guide
Three similar-looking units, three different meanings
A US A1C report usually shows a percentage, such as 7.0%. That is the NGSP/DCCT-aligned way to report how much hemoglobin is glycated. An international report may show the same result as 53 mmol/mol under the IFCC system. These two numbers describe the same HbA1c test.
Glucose is different. US meters and lab reports commonly use milligrams per deciliter (mg/dL), while many countries use millimoles per liter (mmol/L). For example, an A1C of 7.0% corresponds to an estimated average glucose of roughly 154 mg/dL or 8.6 mmol/L. The 53 mmol/mol HbA1c result must not be read as 53 mmol/L glucose.
A1C (%)
NGSP/DCCT HbA1c format used in the United States.
HbA1c (mmol/mol)
IFCC format used on many international lab reports.
Glucose (mmol/L)
A glucose concentration used by meters, CGMs, and laboratories.
The NGSP-to-IFCC formula
The converter uses the relationship published by the NGSP for translating standardized HbA1c results. To convert a percentage into mmol/mol, subtract 2.152 from the percentage and divide by 0.09148. The result is rounded to the nearest whole mmol/mol, matching the way this unit is commonly reported.
For 7.0%, the calculation is (7.0 − 2.152) ÷ 0.09148 = 52.99, reported as 53 mmol/mol. Conversion is not a new test result; it is a different expression of the same standardized HbA1c value.
A1C conversion chart
This table keeps HbA1c conversion and estimated glucose in separate columns. eAG values come from the ADAG relationship and are population-based estimates, not measured daily averages.
| A1C (%) | HbA1c (mmol/mol) | eAG (mg/dL) | eAG (mmol/L) |
|---|---|---|---|
| 4 | 20 | 68 | 3.8 |
| 5 | 31 | 97 | 5.4 |
| 5.7 | 39 | 117 | 6.5 |
| 6 | 42 | 126 | 7 |
| 6.5 | 48 | 140 | 7.8 |
| 7 | 53 | 154 | 8.6 |
| 8 | 64 | 183 | 10.2 |
| 9 | 75 | 212 | 11.8 |
| 10 | 86 | 240 | 13.3 |
| 11 | 97 | 269 | 14.9 |
| 12 | 108 | 298 | 16.5 |
Need a broader reference? See the complete A1C chart or calculate A1C to blood sugar with more interpretation guidance.
HbA1c conversion is exact; eAG is an estimate
NGSP percentage and IFCC mmol/mol are standardized reporting systems linked by a master equation. Estimated average glucose is a separate translation intended to make A1C easier to relate to glucose readings. It uses the ADAG equation: eAG in mg/dL = 28.7 × A1C − 46.7. Dividing mg/dL by about 18 gives mmol/L.
A person’s actual meter or CGM average may not match eAG. A1C is influenced by glucose exposure and the lifespan of red blood cells, while a device average depends on which readings were captured. Sparse checks taken mainly before meals may miss after-meal highs or overnight lows. CGM data offer more coverage but still depend on sensor wear and data quality.
When the number needs clinical context
A calculator cannot determine whether an A1C is reliable for you. Conditions that alter red-blood-cell turnover can make the test appear higher or lower than expected. Hemoglobin variants can interfere with some assay methods. Pregnancy, anemia, kidney disease, recent blood loss, transfusion, or treatment that changes red-cell production can also matter.
Do not change insulin or other medication based on a converted value. If A1C conflicts with symptoms, home readings, or CGM patterns, take both records to a qualified clinician. The issue may be data coverage, test timing, a medical condition, or the laboratory method—not a simple arithmetic error.
How to use the result without creating confusion
1. Copy the original
Enter the A1C percentage exactly as the laboratory reported it. Avoid converting an already converted value.
2. Check the denominator
HbA1c uses mmol/mol. A glucose result uses mmol/L. One word in the unit makes a major difference.
3. Round at the end
Keep the original percentage during calculation, then report IFCC HbA1c as a whole mmol/mol unless your laboratory specifies otherwise.
4. Label shared records
When messaging a clinician or adding a personal note, include the number, unit, test date, and whether the glucose value is estimated.
Questions about A1C units
Is mmol/mol the same as mmol/L?
No. mmol/mol reports HbA1c using the IFCC system. mmol/L reports glucose concentration. The similar abbreviations describe different measurements and cannot be swapped.
What is 7% A1C in mmol/mol?
Using the NGSP–IFCC master equation, 7.0% is approximately 53 mmol/mol. The related estimated average glucose is about 154 mg/dL or 8.6 mmol/L.
Why does my US report use a percentage?
US laboratories generally report HbA1c in NGSP/DCCT-aligned percentage units. Many countries use IFCC mmol/mol. Both describe glycated hemoglobin and can be converted mathematically.
Does converting A1C change its clinical meaning?
No. Unit conversion changes how the same laboratory result is written. It does not improve the test, change the underlying value, or replace interpretation by your clinician.
Can I convert one finger-stick value into A1C?
No. A finger-stick is one moment in time, while A1C reflects longer-term glucose exposure. An average made from enough meter or CGM data can produce an estimate, but it is not a laboratory A1C.
Why might A1C and my meter average disagree?
Meter timing and data gaps can affect the average. Anemia, altered red-blood-cell lifespan, hemoglobin variants, kidney disease, pregnancy, recent blood loss, or transfusion can also affect A1C interpretation.
Sources and review notes
Formulas and interpretation notes are based on the NGSP HbA1c converter and master equation, the ADAG study published in Diabetes Care, and NIDDK guidance on the A1C test. Reviewed August 15, 2026. This educational tool does not diagnose diabetes or set an individual treatment target.