Insulin-to-Carb Ratio and Correction Factor Calculator
Calculate insulin-to-carb ratio (ICR), correction factor, and mealtime insulin dose.
Estimates blood sugar correction for Type 1 and Type 2 diabetes management.
MEDICAL DISCLAIMER This calculator is for educational purposes only. Always follow your doctor’s or certified diabetes educator’s prescribed ratios and correction factors. Never adjust insulin without medical supervision.
Insulin-to-Carb Ratio (ICR) ICR tells you how many grams of carbohydrate 1 unit of rapid-acting insulin covers. ICR = 500 / Total Daily Dose (TDD) of insulin (the “500 Rule”) Example: TDD = 40 units → ICR = 500/40 = 12.5 → 1 unit covers 12.5g carbs. More sensitive patients (low TDD): higher ICR (fewer units for same carbs). More resistant patients (high TDD): lower ICR (more units per gram of carbs). Children often have higher ICR (1:20–1:30); adults often 1:10–1:15.
Correction Factor (Insulin Sensitivity Factor, ISF) ISF tells you how much 1 unit of rapid-acting insulin lowers blood sugar. ISF = 1700 / TDD (mg/dL scale) or ISF = 94 / TDD (mmol/L scale) Example: TDD = 40 → ISF = 1700/40 = 42.5 mg/dL per unit. 1 unit lowers blood glucose by ~42.5 mg/dL (or 2.4 mmol/L). Also called “correction factor” or “sensitivity factor.”
Meal Bolus (Mealtime Insulin Dose) Carb dose = Carbs eaten / ICR Correction dose = (Current BG − Target BG) / ISF Total meal bolus = Carb dose + Correction dose (or − correction if BG is low)
Target Blood Glucose ADA recommends pre-meal target: 80–130 mg/dL (4.4–7.2 mmol/L). 2-hour post-meal: < 180 mg/dL (< 10 mmol/L). Individual targets vary — set by your endocrinologist.
How we build and check this calculator
This calculator runs entirely in your browser, so the numbers you enter stay on your device. The math behind it is written by hand and tested against worked examples and standard references before the page goes live.
SuperGlobalCalculator is independently built and maintained. See how we build and verify our calculators.