A1C Calculator

A1C Calculator for Endocrinology. The result translates units of discussion, not a treatment target. ADA 2026 recommends individualized glycemic goals, taking hypoglycemia, health status, treatment burden, and preferences into account. A high eAG alone does not establish that treatment should be intensified.

For shared guidance on choosing a tool and documenting results, read the clinical calculator workflow.

How this calculator works

The ADAG regression translates HbA1c into estimated average glucose: eAG in mg/dL = 28.7 x HbA1c (%) - 46.7. This implementation divides that result by 18.0182 for mmol/L and displays both units. It accepts a percentage, not an IFCC result in mmol/mol. The calculation estimates a population relationship; it does not measure this individual's glucose.

When to use this calculator

Use as a communication aid when discussing a laboratory HbA1c. Check that the assay and red-cell context make HbA1c interpretable, then compare with glucose records covering a similar period. Do not use the conversion to diagnose diabetes or calculate an insulin dose.

Inputs used

  • Laboratory HbA1c in percent

Clinical interpretation

The result translates units of discussion, not a treatment target. ADA 2026 recommends individualized glycemic goals, taking hypoglycemia, health status, treatment burden, and preferences into account. A high eAG alone does not establish that treatment should be intensified.

Worked example

HbA1c 8.0% gives 28.7 x 8 - 46.7 = 182.9 mg/dL. Dividing by 18.0182 gives 10.151 mmol/L, displayed as 10.2 mmol/L (183 mg/dL). The separately rounded published SI regression gives a slightly different last decimal. At 7.0%, the unrounded result is 154.2 mg/dL, displayed as 154.

Limitations and safety notes

HbA1c can be misleading with altered red-cell survival, recent transfusion, or assay interference. Effects of hemoglobin variants depend on the assay and condition; they do not make every HbA1c universally invalid. Averages hide hypoglycemia and variability. The input range extending to 20% is a software range, not proof that ADAG is reliable at that extreme. No fixed individual error margin is supplied.

Frequently asked questions

Can I enter HbA1c in mmol/mol?

No. This field expects the percentage. A value reported in mmol/mol requires a separate HbA1c unit conversion, not a glucose conversion.

Does 183 mg/dL mean glucose stayed near that value?

No. It is an estimate derived from HbA1c. Glucose traces are needed to see low readings, peaks, and day-to-day variation.

References

  • Nathan DM et al. Translating the A1C assay into estimated average glucose values. Diabetes Care. 2008. PMID: 18540046. https://pubmed.ncbi.nlm.nih.gov/18540046/
  • ADA Professional Practice Committee. Glycemic Goals, Hypoglycemia, and Hyperglycemic Crises: Standards of Care in Diabetes-2026. https://doi.org/10.2337/dc26-S006

Editorial review and citation methodology

Maintained by the Quick Medical Calculator Editorial Team. Content record date: September 7, 2026. A content date is not evidence of independent clinical review. Individual clinical sign-off is not recorded on this page.

  • Prefer original validation studies for scoring systems and prediction tools.
  • Use current specialty society guidance, transplant allocation policy, public health guidance, or regulator resources when they govern clinical use.
  • Include limitations and safety notes when a calculator is population-specific, context-dependent, or unsuitable as a standalone decision tool.

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