4 Free Diabetes Calculators to Bookmark in 2026

Blood sugar converter, A1C calculator, insulin correction factor, and carb counter — free online tools for diabetes management.

Managing diabetes means working with numbers every day — blood sugar readings, A1C percentages, insulin doses, and carbohydrate grams. We built four free calculators to make these calculations faster and more accurate.

1. Blood Sugar Unit Converter (mg/dL ↔ mmol/L)

If you switch between US and international sources, you have probably seen both mg/dL and mmol/L. Our [blood sugar converter](/tools/blood-sugar-converter) handles the conversion instantly in both directions, and shows you where your reading falls in the normal, prediabetes, and diabetes reference ranges.

2. A1C Calculator

Your A1C reflects average blood sugar over the past 2–3 months. Our [A1C calculator](/tools/a1c-calculator) uses the ADA ADAG formula to estimate your A1C from average glucose — or reverse it to see what average glucose corresponds to any A1C target. Includes an eAG reference table from A1C 5% through 12%.

3. Insulin Correction Factor Calculator

The 1800 Rule gives you a starting estimate of your insulin sensitivity factor — how many mg/dL one unit of rapid-acting insulin will lower your blood sugar. Our [correction factor calculator](/tools/insulin-correction-factor) supports both the 1800 Rule (rapid-acting) and the 1500 Rule (regular insulin), in mg/dL or mmol/L. It also calculates your correction dose when blood sugar is above target.

4. Carb Counter & Glycemic Index Chart

Knowing the carb content and glycemic index of foods helps you predict blood sugar impact before you eat. Our [carb counter and GI chart](/tools/carb-counter) covers 70+ common foods across 9 categories with real-time search, category filter, sort by GI or carbs, and a per-100g toggle.

How to Use These Tools Together

Use the carb counter before meals to plan low-GI choices. After eating, log your glucose in Glucoly and note the spike. Over weeks, your average glucose feeds into the A1C calculator for a trend estimate. If your doctor adjusts your insulin, recalculate your correction factor with the updated total daily dose.

Frequently Asked Questions

Are these calculators medically accurate?

These tools use standard formulas referenced by the American Diabetes Association and peer-reviewed research. However, they are for educational purposes only — always verify results with your healthcare provider and do not adjust medications without medical guidance.

Do I need to create an account to use these tools?

No. All four calculators are completely free to use with no registration required. For logging and tracking your results over time, download the Glucoly app.

What other tools are you planning?

We are working on a BMI and ideal weight calculator, a diabetes risk assessment quiz, and a meal glycemic load estimator. Download Glucoly to stay updated.

Sources

• American Diabetes Association. Standards of Medical Care in Diabetes 2024. Diabetes Care 2024;47(Suppl 1).
• Nathan DM, et al. Translating the A1C assay into estimated average glucose values. Diabetes Care. 2008;31(8):1473-1478.
• Atkinson FS, Foster-Powell K, Brand-Miller JC. International Tables of Glycemic Index and Glycemic Load Values: 2008. Diabetes Care. 2008;31(12):2281-2283.
• Walsh J, Roberts R, Bailey T. Guidelines for Optimal Bolus Calculator Settings in Adults. J Diabetes Sci Technol. 2011;5(1):129-135.

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