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A1C Calculator

Source: Nathan DM, Kuenen J, Borg R, Zheng H, Schoenfeld D, Heine RJ. Translating the A1C Assay Into Estimated Average Glucose Values. Diabetes Care 2008;31(8):1473-1478 (ADAG Study Group) · Source verified August 22, 2026

Blake Boege
Written by Blake Boege · Founder, Calculator Answers

An A1C calculator is a medical conversion tool that translates estimated average glucose (eAG) levels from daily blood sugar monitoring into an approximate Hemoglobin A1c percentage, or vice versa. The conversion uses the regression published by the ADAG Study Group in Diabetes Care in 2008: eAG (mg/dL) = 28.7 × A1C − 46.7, fitted with an R-squared of 0.84. It helps diabetic patients correlate their daily glucometer readings with their long-term A1C lab results.

Convert between A1C percentage and average blood glucose (mg/dL or mmol/L). Includes diabetes risk categories.

Quick Answer

Convert your estimated average glucose (eAG) readings into an estimated A1C percentage. Useful for diabetic patients tracking blood sugar between lab visits.

%

Usually between 4.0 and 14.0

Estimated Average Glucose

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How it works

We use the official formula from the American Diabetes Association's ADAG study to convert between A1C and estimated Average Glucose (eAG).

eAG (mg/dL) = (28.7 × A1C) − 46.7

A1C (%) = (eAG + 46.7) ÷ 28.7

Medical Disclaimer

This calculator provides estimates based on standard conversion formulas. Results are for educational purposes only and not a substitute for medical advice, diagnosis, or treatment. Discuss your A1C results with a qualified healthcare provider.

What is A1C?

A1C (also called HbA1c or glycated hemoglobin) is a blood test that measures the percentage of hemoglobin in your blood that has glucose attached to it. Since red blood cells live about 3 months, A1C reflects your AVERAGE blood sugar over the past 2-3 months — not just the moment of the test.

WHY IT MATTERS:

  • More reliable than a single blood sugar reading (which can be affected by recent meals, stress, exercise, illness)
  • Used to diagnose prediabetes and diabetes
  • Used to monitor how well diabetes is being managed
  • Doesn't require fasting before the test

HOW IT'S MEASURED:

  • A1C is reported as a percentage in the US
  • Some countries use mmol/mol (IFCC units): an A1C of 6.5% equals about 48 mmol/mol
  • The calculator above converts between A1C and average glucose in both common units

NORMAL VS. ELEVATED A1C:

  • Below 5.7% — below the ADA prediabetes criterion. The ADA does not publish a label for this region; the word normal is this page's, not the ADA's.
  • 5.7% to 6.4%: Prediabetes — elevated risk, lifestyle changes recommended
  • 6.5% and above: Diabetes — an ADA diagnostic criterion, requiring an NGSP-certified, DCCT-standardized laboratory method, and in the absence of unequivocal hyperglycaemia two abnormal results from different tests

For most adults with diagnosed diabetes, the management target is below 7% — though individual goals vary based on age, other health conditions, hypoglycemia risk, and how long someone has had diabetes.

How A1C relates to average glucose

The American Diabetes Association uses this formula to convert between A1C and estimated average glucose (eAG):

FORMULA: eAG (mg/dL) = (28.7 × A1C) - 46.7

CONVERSION TABLE:

A1C (%)Average Glucose (mg/dL)Average Glucose (mmol/L)
5.0%975.4
5.5%1116.2
6.0%1267.0
6.5%1407.8
7.0%1548.6
7.5%1699.4
8.0%18310.2
8.5%19711.0
9.0%21211.8
10.0%24013.4
11.0%26914.9
12.0%29816.5

USEFUL FOR:

  • Comparing finger-stick or CGM (continuous glucose monitor) averages to expected A1C
  • Setting glucose targets based on A1C goals
  • Understanding what your daily blood sugar should average to hit a target A1C

LIMITATIONS:

  • The eAG formula is a statistical average; individual results may vary
  • A1C and average glucose can disagree in certain medical conditions (anemia, kidney disease, recent transfusion, hemoglobin variants)
  • Recent significant changes in glucose levels may not yet be reflected in A1C

Lowering A1C

For prediabetes and diabetes, lowering A1C reduces the risk of complications. Even small reductions matter — a 1% drop in A1C reduces diabetes complication risk by approximately 21%.

LIFESTYLE STRATEGIES:

DIET:

  • Reduce refined carbs and added sugars (sodas, candy, white bread, pastries)
  • Increase fiber (vegetables, whole grains, legumes)
  • Choose lean proteins and healthy fats
  • Watch portion sizes — even healthy carbs raise blood sugar
  • Consider the timing and balance of meals

PHYSICAL ACTIVITY:

  • Aim for 150+ minutes of moderate activity per week
  • Both aerobic exercise and resistance training help
  • Exercise improves insulin sensitivity for hours afterward
  • Even short walks after meals can lower post-meal glucose spikes

WEIGHT MANAGEMENT:

  • Losing just 5-7% of body weight significantly improves blood sugar
  • This is a target weight loss in the landmark Diabetes Prevention Program study
  • Sustainable, gradual weight loss is more effective than crash diets

SLEEP AND STRESS:

  • Poor sleep raises cortisol and increases insulin resistance
  • Aim for 7-9 hours of quality sleep
  • Chronic stress raises blood sugar — meditation, exercise, and counseling help

MEDICATIONS (when needed):

  • Metformin is the most common first-line medication for type 2 diabetes
  • Many other classes available: SGLT2 inhibitors, GLP-1 agonists (like Ozempic, Wegovy), DPP-4 inhibitors, sulfonylureas, insulin
  • Your doctor will tailor medications to your specific situation

MONITORING:

  • A1C is typically checked every 3-6 months
  • Daily glucose monitoring (fingersticks or CGM) helps identify patterns
  • Track foods, exercise, and medications alongside glucose to see what works

When A1C may not be accurate

A1C is reliable for most people, but certain conditions can throw off results:

CONDITIONS THAT FALSELY ELEVATE A1C:

  • Iron deficiency anemia (red blood cells live longer, accumulate more glucose)
  • Vitamin B12 deficiency
  • Chronic kidney disease (uremia)
  • Some hemoglobin variants
  • Splenectomy (spleen removal)

CONDITIONS THAT FALSELY LOWER A1C:

  • Hemolytic anemia (red blood cells destroyed faster, less time to glycate)
  • Recent blood transfusion
  • Pregnancy (red blood cell turnover faster)
  • Sickle cell disease and other hemoglobinopathies
  • Recent significant blood loss
  • Certain medications (high-dose vitamin E, ribavirin)

WHEN A1C MIGHT DISAGREE WITH FINGERSTICK READINGS:

  • If your daily glucose averages don't match your A1C, talk to your doctor
  • Alternative tests: fructosamine (reflects 2-3 weeks), glycated albumin
  • CGM (continuous glucose monitor) data may be more accurate for daily management

ALWAYS CONFIRM A DIAGNOSIS:

  • A single A1C of 6.5% or higher should be confirmed with a repeat test
  • The American Diabetes Association requires two abnormal results (either A1C, fasting glucose, or oral glucose tolerance test) for a formal diagnosis
  • If results conflict, additional testing helps clarify

Interpreting your A1C result

A1C BELOW 5.7%: Normal

  • Diabetes risk is low
  • Maintain healthy eating, exercise, and weight
  • Continue regular checkups; some people develop diabetes risk factors as they age

A1C 5.7% to 6.4%: PREDIABETES

  • Elevated diabetes risk. Tabak and colleagues, writing in The Lancet in 2012, report that "around 5-10% of people with prediabetes become diabetic annually although conversion rate varies by population characteristics and the definition of prediabetes". This figure is frequently credited to the CDC, whose prediabetes page carries no annual conversion rate at all. Do not confuse it with the lifetime figure from the same paper, which is much larger.
  • The GOOD news: prediabetes is often reversible with lifestyle changes
  • The CDC's Diabetes Prevention Program reduces diabetes risk by ~58% with weight loss and exercise
  • Action plan: 5-7% body weight loss, 150+ minutes weekly exercise, less added sugar, more fiber

A1C 6.5% to 7.0%: DIABETES (well-controlled or new)

  • Initial target for most diabetics is below 7%
  • Lifestyle interventions are critical
  • Medications often added if lifestyle alone doesn't reach target

A1C 7.0% to 8.0%: DIABETES (moderately controlled)

  • Increased risk of long-term complications
  • Treatment intensification often warranted
  • Discuss medication adjustments with your doctor

A1C 8.0% to 9.0%: DIABETES (poorly controlled)

  • Significant risk of complications
  • Likely needs medication changes
  • Possible need for more intensive monitoring

A1C ABOVE 9.0%: DIABETES (very poorly controlled)

  • High risk of immediate and long-term complications
  • Urgent treatment plan needed — usually multiple medications including possibly insulin
  • See an endocrinologist if not already

INDIVIDUAL TARGETS VARY:

  • Older adults or those with multiple health conditions may have less stringent targets. The ADA Standards of Care recommend individualised goals, with less stringent ones such as A1C below 8.0% for people with significant cognitive or functional limitations, frailty, severe comorbidities, or where life expectancy means the benefit of a tighter goal may not be realised
  • Young, otherwise-healthy people may target lower (under 6.5%)
  • Pregnant women have stricter targets
  • Discuss your specific target with your doctor

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Frequently asked questions

A1C (also called HbA1c) is the percentage of hemoglobin in your blood with glucose attached. Since red blood cells live about 3 months, A1C reflects your average blood sugar over that period. It's used to diagnose diabetes and prediabetes, and to track how well diabetes is being managed.

Use the formula: Average Glucose (mg/dL) = (28.7 × A1C) - 46.7. It is not a rule of thumb: it is the regression Nathan and colleagues published in Diabetes Care in 2008 from the A1c-Derived Average Glucose study, which reported it as "AG mg/dl = 28.7 × A1C − 46.7, R 2 = 0.84". Two things travel with it that this page will not drop. The paper prints the same regression in both units, "AGmg/dl=28.7 × A1C − 46.7 (AGmmol/l=1.59 × A1C − 2.59)", with fuller coefficients of 1.5944 and 2.594 in its table footnote, and those are 28.7 and 46.7 divided by 18 to the digit. So the mmol form is a unit conversion using a divisor of 18, not a second fit. That matters because this page used to convert with 18.0182, the more precise molar factor, which disagreed with the paper's own table in the last digit at three A1C values; it now uses the published coefficients so the column matches the source it cites. And the paper reports a standard deviation of prediction error of 15.7 mg/dL, publishing a 95% interval of 123 to 185 around the 154 that an A1C of 7 gives. For example, an A1C of 7% equals about 154 mg/dL. The calculator above does this conversion both ways. Multiply mg/dL by 18.0182 to convert to mmol/L (international units).

The American Diabetes Association Standards of Care define A1C 5.7 to 6.4 percent as a criterion for prediabetes and A1C at or above 6.5 percent as a criterion for diabetes, with the condition that the test be run in a laboratory using an NGSP-certified method standardized to the DCCT assay, and that in the absence of unequivocal hyperglycaemia a diagnosis needs two abnormal results. Note what the ADA does NOT say: it defines those two categories affirmatively and does not label the region below 5.7 percent at all. Calling it normal is an inference from the boundary, not an ADA statement, and this page marks it as such. For most adults already diagnosed with diabetes the management target is below 7 percent, and individual goals vary.

Lifestyle changes — reducing refined carbs, increasing fiber, regular exercise (150+ min/week), losing 5-7% of body weight, getting adequate sleep, and managing stress. Medications are added if lifestyle alone isn't enough. Even a 1% drop in A1C cuts complication risk by about 21%.

For those with diabetes: every 3-6 months. For those without diagnosed diabetes but with risk factors: at least every 3 years, or more often based on doctor's advice. Prediabetics often get tested annually. The frequency depends on how well-controlled blood sugar is and what changes you're making.

Yes — in certain conditions. Falsely high results: iron deficiency anemia, kidney disease. Falsely low results: hemolytic anemia, recent blood transfusion, pregnancy, sickle cell disease. If your daily glucose readings don't match your A1C, talk to your doctor about alternative tests like fructosamine.

No — that's actually an advantage of the A1C test. Because it measures a 2-3 month average, recent meals don't significantly affect the result. You don't need to fast for an A1C test, unlike a fasting glucose test.

A1C measures average glucose over 2-3 months and doesn't require fasting. Fasting glucose measures your blood sugar at a single point after not eating for 8+ hours. Both are used for diabetes diagnosis: fasting glucose ≥126 mg/dL or A1C ≥6.5% indicates diabetes.

Yes — home A1C test kits are available at pharmacies and online (typically $25-$50). They give a result within minutes from a finger-stick blood sample. However, home tests may not be as accurate as lab tests. Use them for general tracking; rely on your doctor's lab tests for diagnosis and major treatment decisions.

The conversion formulas come directly from the American Diabetes Association's ADAG (A1C-Derived Average Glucose) study. The math is exact, but individual results may vary because the formulas represent statistical averages. Always interpret your results in consultation with your healthcare provider.