Carbohydrate Counter Calculator

An insulin-to-carb ratio is the number of carbohydrate grams covered by one unit of rapid-acting insulin. Ratios vary widely by person, time of day, activity, illness, and delivery method. The calculator performs arithmetic only with a ratio already prescribed by your diabetes team. Do not use population examples or this tool to create or change an insulin dose.

A correction factor estimates how much one unit of rapid-acting insulin lowers glucose. It must be individualized and can change with time of day, activity, illness, hormones, insulin on board, and delivery system. Use only the factor prescribed by your diabetes team. This calculator must not be used to derive a factor or change a correction dose.

Net carbs equal total carbohydrates minus fiber. Insoluble fiber is not digested into glucose, so subtracting it gives a better estimate of glycemic load for low-carb and ketogenic eaters; the ketogenic-meal threshold of net carbs below 20 g uses the same convention. Many T1D clinicians, however, recommend dosing for total carbs unless a single food contains more than about 5 g of fiber, because partial fermentation of soluble fiber can still raise glucose over hours. The calculator makes the choice explicit: tick the box only if your care team has agreed that net carbs are appropriate for your dosing.

The 15-15 rule is the ADA's standard for treating mild-to-moderate hypoglycemia (blood glucose at or below 70 mg/dL): eat 15 g of fast-acting carbohydrate (4 glucose tablets, half a cup of juice or regular soda, or 1 tablespoon of sugar or honey), wait 15 minutes, and recheck. If glucose is still below 70 mg/dL, treat with another 15 g and recheck. Once back above 80 mg/dL, eat a small snack with protein and slower-acting carbs if your next meal is more than 1 hour away. Severe hypoglycemia (unable to swallow safely) needs glucagon and emergency care, not the 15-15 rule.

In type 1 diabetes (T1D) the pancreas makes no insulin, so every gram of digested carbohydrate must be matched with injected or pumped insulin to avoid postmeal hyperglycemia. The landmark DCCT trial (Diabetes Control and Complications Trial, NEJM 1993) showed that intensive insulin therapy with carb-matched dosing lowered A1C by about 1.7 percentage points compared with conventional fixed dosing, and cut retinopathy, nephropathy, and neuropathy risk by 35 to 76% over a decade of follow-up. Modern hybrid closed-loop pumps still depend on the user entering carb counts to dose meal boluses. Accurate carb counting (within plus or minus 10 g per meal) plus a well-tuned ICR is the single biggest lever a T1D patient has over time-in-range.