Inputs
What the formulas mean
Base ratio: ICR = C ÷ TDD, where C is 500 (rapid‑acting), 450 (regular), or a custom constant.
Time adjustment: Dose = Carbs ÷ ICR × Multiplier. Equivalently, ICRadj = ICR ÷ Multiplier.
Example: TDD 40, rapid‑acting → base ICR = 500 ÷ 40 = 12.5 g/unit. Dinner (×1.2) → adjusted ICR ≈ 10.4 g/unit.
Educational information only. This does not provide medical advice. Verify settings with your diabetes care team.
FAQs
It estimates how many grams of carbohydrate are covered by one unit of rapid‑acting insulin. For example, an ICR of 12 means 1 unit covers about 12 grams of carbohydrate.
Both divide a constant by total daily dose. The 500 rule is commonly used for rapid‑acting analogs; the 450 rule is an older heuristic for regular insulin. Clinicians personalize beyond these approximations.
Insulin needs may vary through the day due to hormones, prior doses, and activity. Some people need relatively more insulin at lunch or dinner than at breakfast.
This tool focuses on meal dosing. Correction dosing requires an insulin sensitivity factor (ISF), which is outside the scope of this page.
Follow your care plan. Some pens and pumps support half‑unit increments, while others use whole units only. The safest option is the one recommended by your clinician.
No. These are educational starting points. Do not change settings without professional guidance. Monitor glucose and be cautious about hypoglycemia.
Insulin needs vary widely in children and during pregnancy. Specialized guidance is essential in these situations.
© 2026 Insulin‑to‑Carb Ratio Calculator. For education only. Not a substitute for professional medical advice, diagnosis, or treatment.