🩺 A1c Calculator
Translate lab-reported HbA1c into everyday glucose numbers, or estimate A1c from CGM and meter data.
Use the percentage from your lab report (e.g., 6.8%).
Formula: eAG (mg/dL) = 28.7 × HbA1c − 46.7 • HbA1c = (eAG + 46.7) ÷ 28.7.
How to Use This Calculator
Choose your direction
Select HbA1c ➜ eAG when you have a lab percentage, or Glucose ➜ HbA1c when you know daily averages from monitoring data.
Enter the value
Input your HbA1c percent or average glucose. Switch units between mg/dL and mmol/L as needed. Then click “Calculate.”
Review and plan
Use the results to discuss targets with your diabetes care team and to adjust lifestyle or medication plans if needed.
Formula
The calculator uses the A1c-Derived Average Glucose (ADAG) equation, validated in the NEJM 2008 multicentre study linking HbA1c to continuous glucose monitoring:
- eAG (mg/dL) = 28.7 × HbA1c − 46.7
- eAG (mmol/L) = (28.7 × HbA1c − 46.7) ÷ 18.0182
- Estimated HbA1c (%) = (eAG (mg/dL) + 46.7) ÷ 28.7
These relationships assume stable red blood cell turnover. Conditions affecting haemoglobin (anaemia, CKD, haemoglobinopathies) can distort HbA1c and should be considered when interpreting results.
Full Description
HbA1c measures the percentage of glycated haemoglobin, providing a long-range view of glycaemic exposure. It is a key marker for diagnosing diabetes (≥6.5%) and monitoring ongoing control. Translating A1c into estimated average glucose helps patients relate lab results to daily readings from meters or CGMs.
A1c alone cannot reveal variability or hypoglycaemia risk. Combine it with time-in-range, fasting glucose, post-meal checks, and symptoms to form a complete picture. Target ranges differ for pregnant individuals, older adults, or those with multiple comorbidities.
Use this calculator for education and planning, recognising that medical decisions—from medication adjustments to pregnancy care plans—should always involve your healthcare professional.
Frequently Asked Questions
What is a good HbA1c target?
Many adults with diabetes aim for <7%. Individual targets may be higher or lower depending on pregnancy, age, risk of hypoglycaemia, and other medical conditions.
Why doesn’t my A1c match my meter readings?
Differences can result from high glucose variability, limited testing times, anaemia, haemoglobin variants, or inaccurate meters. Discuss discrepancies with your clinician.
Can A1c be too low?
Very low A1c (<5%) may reflect recurrent hypoglycaemia or conditions affecting red blood cells. Report symptoms such as faintness or confusion to your healthcare team.
Is A1c accurate during pregnancy?
HbA1c may be lower in pregnancy due to increased red blood cell turnover. Obstetric teams prioritise glucose profiles and target ranges tailored to gestational age.
How often should I test A1c?
Typically every 3 months when adjusting therapy, and every 6 months when stable. Your clinician may recommend more frequent checks in certain situations.