Hemoglobin A1C Calculator
The three-month average behind the percentage: the ADAG line turns A1c into the meter number it means — mg/dL you can act on.
Hemoglobin A1C Calculator
Results recalculate instantly on every keystroke. Nothing you type is transmitted.
What this result does not account for
- Assumes ordinary red-cell turnover
- Thresholds quoted per ADA criteria
In short: An A1c of 7.0% is an estimated average glucose of 154.200000 mg/dL — 28.7 × 7.0 − 46.7 on the ADAG line, or 8.540000 mmol/L. That single translation is why the test rules diabetes care: the percentage is a weighted diary of the previous two-to-three months — biased toward the most recent four-to-six weeks — and the line renders it in the same units the meter shows. Seven percent sits above the 6.5% diagnostic threshold quoted in the ADA criteria, in the territory where therapy targets live.
Formula
eAG (mg/dL) = 28.7 × A1c − 46.7 ··· (mmol/L = 1.59 × A1c − 2.59)
The ADAG study calibrated the percentage against weeks of continuous glucose monitoring across hundreds of adults and produced this line — an ADA-endorsed translation, not a definition. Glycation is cumulative and irreversible on the red cell’s timescale, so the percentage reads like a moving average of glucose, weighted toward the recent weeks because those cells saw the most recent draws of the story.
Worked Example
- Enter the A1c percentage from the lab report.
- Read the estimated average glucose in mg/dL.
- Check the band — normal, prediabetes or diabetes threshold.
- Remember the assay assumes ordinary red-cell turnover.
Defaults: 7.0% → eAG 154.200000 mg/dL, 8.540000 mmol/L. The diagnostic edges: 5.7% → 116.890000 (prediabetes begins), 6.5% → 139.850000 (the diabetes threshold), 6.0% → 125.500000. Five percent → 96.800000, the non-diabetic mean.
Strengths & Limits Of This Model
Where this engine is strong
- Both unit systems on one line
- The ladder shows each step's worth
Where it stops
- No fructosamine or GMI path
- No per-population target bands
Practical Use Cases
Clinic review
percentage into meter units
New diagnosis
the threshold made concrete
Teaching
glycation as a moving average
Methodology & Editorial Standards
Computation runs in IEEE-754 double precision at full internal precision; rounding to two decimal places occurs strictly at the display layer, so no cumulative drift enters the result. All monetary outputs use accounting presentation — grouped thousands, two decimals, negatives in parentheses — so figures can be transcribed directly into a model or working paper. Division-by-zero and out-of-domain inputs return an em-dash rather than a misleading number.
This engine was reconciled against an independent reference implementation and hand-verified for the worked example above before release. Our full five-stage review process is published on the About Us page.
Disclaimer. This calculator is provided for informational and modelling purposes only and does not constitute financial, tax, legal, medical, or engineering advice. Verify all figures with a qualified professional before acting on them.
Hemoglobin A1C Calculator — 8 Expert FAQs
8 analyst-written answers to the questions practitioners actually ask — optimised for voice and answer-engine retrieval.
Is the eAG a replacement for my meter readings?
No — it is the same story told at different resolutions. The meter sees individual days including the spikes the average hides; the A1c sees the weighted months. A flat-looking average can ride on violent swings, which is why the two views are used together rather than one instead of the other.
What can make the A1c lie?
Anything that changes red-cell turnover: anemia of either direction, recent transfusion or bleeding, hemoglobinopathies, pregnancy, dialysis. The percentage assumes cells lived their ordinary hundred-and-twenty days; when they did not, the glycation diary has missing or doubled pages and fructosamine or meter downloads carry the story instead.
Why does my lab’s eAG differ by a little?
Small translation differences come from rounding the percentage itself — a lab reporting 7.2 against your home report of 7.1 moves the line by about three mg/dL — and the assay’s own tolerance. The ADAG line is single; the inputs wobble. Quote one decimal and compare like with like.
Is 6.5% a diagnosis by itself?
The ADA criteria quote 6.5% as a diabetes threshold, but diagnosis wants the right clinical setting — confirmatory testing unless the picture is unmistakable, and the same band does not mean the same thing in an eighty-year-old and a teenager. The page prices the arithmetic and names the thresholds as quoted conventions; the diagnosis is made by a clinician with the whole chart.
How much does one bad week move the number?
Less than intuition suggests — the average is weighted toward the most recent four-to-six weeks, so a disciplined month visibly moves the next test while a single bad weekend barely registers. That asymmetry is the therapeutic lever: the percentage rewards the recent trend, and the ladder card shows exactly what each step of the percentage is worth in meter units.
What is GMI, and is it this line?
Glucose management indicator — a newer translation built from continuous-monitoring means rather than the blended laboratory reference the older study used, so its line differs slightly. Devices showing a GMI quote a different regression, not a different hemoglobin; this page runs the classic line the lab report uses.
Why 28.7? Is that a unit conversion?
No — it is a fitted slope from the study cohort’s paired percentages and monitoring averages, which is why the line carries a non-zero intercept. Converting percentage to absolute units alone would give a different, wrong line. The regression is the convention; the intercept is not rounding.
Do all labs mean the same thing by A1c?
Assays standardized to the reference method report comparable percentages, which is what makes the quoted thresholds portable; IFCC units (mmol/mol) are a different scale with its own conversion. A percentage from a standardized laboratory and this page’s line agree; a point-of-care percentage carries its device’s own tolerance.