Average Blood Sugar Calculator
Average several blood glucose readings and estimate the matching HbA1c. Enter up to five mg/dL readings and this calculator returns the mean, an estimated HbA1c percentage, and the average in mmol/L.
Formula
Average = sum of readings ÷ count; HbA1c% = (average + 46.7) ÷ 28.7
- The average is simply the sum of all the readings you enter divided by how many you entered (blank or zero readings are ignored).
- Estimated HbA1c uses the ADAG relationship: A1c% = (average mg/dL + 46.7) ÷ 28.7.
- To convert mg/dL to mmol/L, divide by about 18.
- A few spot readings are a rough proxy — a lab HbA1c reflects roughly three months of average glucose far more reliably.
- Use this as an educational estimate, not a diagnosis; discuss targets with your doctor.
Three readings: 120, 150, 110 mg/dL
Inputs
- Reading 1: 120 mg/dL
- Reading 2: 150 mg/dL
- Reading 3: 110 mg/dL
- Reading 4: 0 mg/dL
- Reading 5: 0 mg/dL
The average is (120 + 150 + 110) ÷ 3 = 127 mg/dL, which estimates an HbA1c of about (127 + 46.7) ÷ 28.7 ≈ 6.0% and an average of roughly 7.0 mmol/L.
Frequently asked questions
How is average blood sugar calculated?
Add up all your glucose readings and divide by the number of readings. Only positive values are counted.
How does average glucose relate to HbA1c?
The ADAG formula estimates it as A1c% = (average mg/dL + 46.7) ÷ 28.7. A lab test remains the gold standard, but this gives a quick approximation.
How many readings should I enter?
More readings spread across different times of day give a more representative average. Even a couple help, but a single value is not very meaningful.
Why convert to mmol/L?
Many countries report glucose in mmol/L rather than mg/dL. Dividing mg/dL by about 18 gives the mmol/L equivalent.
Is this a substitute for a lab A1c?
No. It is an estimate from limited readings. A laboratory HbA1c reflects your true ~3-month average and should guide treatment.
Related calculators
HbA1c to Average Glucose Calculator HbA1c to Average Glucose Calculator is a health and wellness calculator that helps you calculate your estimated average glucose (eAG) from your HbA1c level. The formula used is: eAG (mg/dL) = 28.7 × HbA1c − 46.7 (ADAG study). Enter values using the units shown next to each input field (e.g. kg, cm, years). Average Glucose to HbA1c Calculator Average Glucose to HbA1c Calculator is a health and wellness calculator that helps you calculate your estimated HbA1c from your average blood glucose level. The formula used is: HbA1c (%) = (average glucose mg/dL + 46.7) ÷ 28.7. Enter values using the units shown next to each input field (e.g. kg, cm, years). Time in Range Calculator Time in Range Calculator is a health and wellness calculator that helps you calculate time in range values from your input data. The formula used is: Daily time in range = (TIR% ÷ 100) × 24 hours. Enter values using the units shown next to each input field (e.g. kg, cm, years).