Enter the amount of carbohydrates in grams and your carb ratio (grams per 1 unit of insulin, g/U) into the calculator to estimate the insulin needed to cover the carbohydrates.

Carb Coverage Calculator

In the Full Bolus tab, active insulin (IOB) is applied to the correction dose only.

Carb Coverage
Full Bolus
Carb Helper

Enter carbs (g) and your carb ratio (g/U) to calculate insulin needed.

Disclaimer: Educational use only; not medical advice. Insulin dosing is individualized—use only clinician-prescribed carb ratio (g/U), target, ISF, and IOB guidance. Do not use this tool in emergencies. If you have symptoms of low blood sugar or your BG is <70 mg/dL (3.9 mmol/L), treat low blood sugar first and follow your care plan; seek urgent care for severe highs with ketones or concerning symptoms. “Carb Helper” food values are approximate—verify with a nutrition label or trusted carb-counting resources. This calculator may store entries in your browser for convenience; avoid shared devices and use “Clear saved data” to remove saved entries.

Related Calculators

Carb Coverage Formula

The following formula is used to calculate the amount of insulin needed to cover the carbohydrates consumed. 

I = C / R

Variables:

  • I is the insulin needed (units)
  • C is the carbohydrates consumed (grams)
  • R is the carb ratio (grams of carbohydrate covered by 1 unit of insulin, g/U)

To calculate the amount of insulin needed, divide the amount of carbohydrates by the carb ratio.

What is Carb Coverage?

Carb coverage is a term used in diabetes management that refers to the amount of insulin required to metabolize a certain amount of carbohydrates. The carb ratio is a crucial component in calculating the correct insulin dose for a meal or snack to maintain blood glucose levels within target ranges.

How to Calculate Carb Coverage?

The following steps outline how to calculate the Carb Coverage.

  1. First, determine the amount of carbohydrates (C) in grams.
  2. Next, determine the carb ratio (R). This is typically the number of grams of carbohydrate covered by 1 unit of insulin (g/U).
  3. Next, gather the formula from above = I = C / R.
  4. Finally, calculate the Insulin Needed (I) in units.
  5. After inserting the variables and calculating the result, check your answer with the calculator above.

Example Problem : 

Use the following variables as an example problem to test your knowledge.

carbohydrates (C) = 60 grams

carb ratio (R) = 15 (15 grams of carbs per 1 unit of insulin, 15 g/U)

insulin needed (I) = 60 ÷ 15 = 4 units