Diabetes Calculators
Free calculators for people living with diabetes and the people who support them: understand an A1c result, convert between mg/dL and mmol/L, summarise your readings, and see how common insulin dosing rules work. Every calculation runs in your browser and nothing is stored.
Understand your numbers
Convert between units and see what a reading or lab result means.
Insulin dosing rules of thumb
Education-only tools that show how common dosing rules work. Your own settings come from your care team.
These tools ask you to confirm you understand they are for education before showing a result. Never change your insulin doses without your care team.
Weight and body shape
Fat around the middle is closely linked with type 2 diabetes, and even modest weight loss can improve blood sugar. These tools help you keep an eye on both.
Key diabetes numbers at a glance
Published thresholds for adults from the American Diabetes Association and the International Consensus on Time in Range. Diagnosis needs confirmed lab tests; targets are set individually.
| Measure | Value |
|---|---|
| Normal fasting glucose | Below 100 mg/dL (5.6 mmol/L) |
| Prediabetes (fasting) | 100 mg/dL (5.6 mmol/L) to 125 mg/dL (6.9 mmol/L) |
| Diabetes range (fasting) | 126 mg/dL (7.0 mmol/L) or higher |
| Normal A1c | Below 5.7% |
| Prediabetes A1c | 5.7% to 6.4% |
| Diabetes range A1c | 6.5% or higher |
| Low blood sugar (level 1) | Below 70 mg/dL (3.9 mmol/L) |
| Serious low (level 2) | Below 54 mg/dL (3.0 mmol/L) |
| Time in range target (70–180 mg/dL) | More than 70% of the time |
Track the numbers behind these calculations
Log glucose readings and insulin doses in FitDose and see estimated A1c, time in range and trends from your own data.
Start logging freeFrequently asked questions
Which calculator should I use?
To understand a lab result, use the A1c calculator. To switch a reading between mg/dL and mmol/L, use the blood sugar converter. If you have a list of readings or a CGM export, the GMI and time in range calculator summarises them. The insulin tools explain dosing rules and are for education only.
What is the difference between A1c, eAG and GMI?
A1c is a lab blood test reflecting roughly the past three months. eAG (estimated average glucose) converts an A1c into an average glucose. GMI works the other way, estimating an A1c from the average of your glucose readings, and was designed for CGM data.
Should I use mg/dL or mmol/L?
Use whichever your meter and care team use. The US and India mostly use mg/dL; the UK, Canada, Australia and much of Europe use mmol/L. Every diabetes calculator here shows both.
Are these calculators medical advice?
No. They explain widely used formulas and published thresholds so you can understand your numbers and talk to your care team. They cannot diagnose diabetes and must not be used to change medication or insulin on your own.
Is anything I enter stored?
No. The calculators run in your browser. Values you type are kept only in the page address so a result can be shared or bookmarked; nothing is sent to or saved on FitDose's servers.
How can I track my numbers over time?
A single calculation is a snapshot. A FitDose account lets you log glucose, insulin doses, weight and measurements, and shows estimated A1c, time in range and trends from your own readings.