Insulin-to-Carb Ratio Calculator

This calculator is for education and planning support. Personal insulin dosing should be confirmed with a qualified clinician, especially for children, pregnancy, illness, or frequent low glucose events.

Calculator Inputs

Meal label

Insulin type

Total daily dose (units)

Meal carbohydrates (grams)

Current glucose (mg/dL)

Target glucose (mg/dL)

Ratio mode

Custom ratio (grams per unit)

Correction mode

Custom correction factor

mg/dL lowered by one unit.

Rounding step (units)

Plotly Graph

The chart compares carb-only insulin with total insulin across rising carbohydrate values. The total line includes the current correction effect.

Example Data Table

Meal	Carbs (g)	Current BG	Target BG	Ratio (g/u)	Correction Factor	Total Bolus (u)
Breakfast	45	160	110	12	45	4.9
Lunch	60	180	110	12	45	6.6
Dinner	75	130	110	10	40	8.0

Formula Used

Estimated insulin-to-carb ratio: 500 ÷ total daily dose for rapid insulin, or 450 ÷ total daily dose for regular insulin.
Estimated correction factor: 1800 ÷ total daily dose for rapid insulin, or 1500 ÷ total daily dose for regular insulin.
Meal insulin: meal carbohydrates ÷ active insulin-to-carb ratio.
Correction insulin: (current glucose − target glucose) ÷ active correction factor.
Total bolus: carb insulin + correction insulin, then rounded to the selected increment.

How to Use This Calculator

Choose rapid acting or regular insulin.
Enter the total daily insulin dose.
Add meal carbohydrates in grams.
Enter the current and target glucose values.
Select estimated or custom ratio mode.
Select estimated or custom correction mode.
Pick a rounding step that matches dosing tools.
Press calculate to view results above the form.
Review the chart, summary table, and export files.

Frequently Asked Questions

1. What does insulin-to-carb ratio mean?

It shows how many grams of carbohydrate are covered by one unit of insulin. A ratio of 12 means one unit covers about 12 grams of carbohydrates.

2. Why does the calculator ask for total daily dose?

Total daily dose helps estimate both the insulin-to-carb ratio and the correction factor. These estimates are common starting points when a personal setting is unavailable.

3. When should I use custom ratio mode?

Use custom mode when a clinician has already prescribed a personal insulin-to-carb ratio. That setting is usually more accurate than a general estimate.

4. What is a correction factor?

A correction factor estimates how much one unit of insulin may lower glucose. It adjusts the meal bolus when current glucose is above or below the target.

5. Why can the correction result be negative?

A negative value means the current glucose is below target. That may suggest less insulin than the meal alone would require, but dosing decisions should still be reviewed carefully.

6. Why is the final dose rounded?

Many pens, syringes, and pumps deliver in fixed steps. Rounding makes the final value easier to match with real dosing hardware.

7. Can this calculator replace medical advice?

No. It is an educational planning tool. Illness, activity, medications, pregnancy, and insulin sensitivity changes can all alter safe dosing needs.

8. What unit does the glucose field use?

This version uses mg/dL. If your readings are in mmol/L, convert them before using the form or adapt the calculator for local units.