How is estimated A1C calculated?

Estimated A1C uses the published ADAG equation from average blood glucose. GMI uses the Bergenstal formula common on CGM AGP reports. Both are estimates, not a lab A1C.

Is this calculator free and private?

Yes. Nothing is stored and you do not need an account. The calculation runs when you enter a number.

What average glucose should I enter?

Use a multi-day average from your meter, CGM, or log when you can. A single reading is a weaker estimate than a longer average.

Estimated A1C calculator

Enter your average glucose to see the A1C and GMI it maps to, using the same published formulas clinicians use. Nothing is stored, and you do not need an account.

Your average glucose

Enter your average glucose to see your estimated A1C and GMI.

Estimated A1C comes from the ADAG equation and GMI from the Bergenstal formula. They answer the same question two ways, so they can differ by a few tenths of a percent. See exactly how we calculate them.

An estimate from a single average is a snapshot. It can hide the highs and lows that a steady record reveals, which is where day-to-day tracking earns its keep.

Prefer to start from the lab value? Every A1C from 4.0% to 14.0% has its own page on the A1C chart, with the average glucose it reflects.

Skip the arithmetic

SteadyRange works out your estimated A1C, GMI, and time in range from your real readings, automatically, and shows the trend over time. Log a reading in seconds, on a private log you control.

Start a free log How we calculate

General information, not medical advice. For plain-language definitions, see the glossary.