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Calculate your bolus insulin dose based on target blood sugar and carbohydrate intake to assist with precise diabetes management.
Arithmetic with prescribed ICR/ISF and consistent glucose units, not an actual injection recommendation; active insulin, exercise and illness are not incorporated. No calculation for low-glucose inputs. Reference
How many grams of carbohydrates 1 unit of insulin can cover
How much blood glucose 1 unit of insulin can lower
Enter data to calculate insulin dose.
Overview
Understand what the tool solves, how it works, and the boundaries of its data.
This calculator lays out two pieces of mealtime insulin arithmetic: carbohydrate coverage and a glucose correction. You enter current and target blood glucose, meal carbohydrate in grams, an insulin-to-carbohydrate ratio (ICR), and an insulin sensitivity factor (ISF). It displays the carbohydrate amount, correction amount, and their combined total in insulin units (U).
ICR describes how many grams of carbohydrate are covered by 1 U of insulin. Enter the denominator: for a prescribed ratio of 1 unit per 15 g, enter 15. ISF describes how much blood glucose 1 U is expected to lower. Its units must match the glucose fields: mg/dL per U with mg/dL values, or mmol/L per U with mmol/L values. These settings and the target must come from an established individual care plan.
Carbohydrate amount (U) = carbohydrate grams ÷ ICR
Correction amount (U) = (current glucose − target glucose) ÷ ISF
Displayed total (U) = the greater of zero or the sum of the two amounts
The correction can be negative when current glucose is below target, reducing the arithmetic total; the total itself is never displayed below zero. Each displayed figure is rounded to one decimal place. Since the total is calculated from the unrounded amounts, adding the two rounded breakdown figures may differ from the rounded total by 0.1 U.
For an arithmetic example only, use mg/dL and enter current glucose 180, target 120, carbohydrate 60 g, ICR 15, and ISF 50 mg/dL per U. The carbohydrate amount is 60 ÷ 15 = 4 U. The correction is (180 − 120) ÷ 50 = 1.2 U. Their sum is 5.2 U. These example values are not suggested treatment settings or a dose recommendation.
Guide
Follow the workflow and verify inputs and outputs with practical examples.
Select mg/dL or mmol/L to match your meter or continuous glucose monitor. Changing this selection clears current glucose, target glucose, and ISF values; it does not convert numbers. Re-enter those fields in the selected unit.
Enter the target, ICR, and ISF provided for the relevant meal or time of day by your diabetes care team. For ICR, enter grams covered by one unit, such as 15 for 1 U per 15 g. Do not derive or guess these settings from this page.
Enter grams of carbohydrate for the meal. A blank carbohydrate field is treated as 0 g. Check the meal estimate and decimal point before reading the result.
Review carbohydrate coverage, correction, and total in U. If no result appears, check that current glucose, target, ICR, and ISF are valid numbers and that ICR and ISF are greater than zero. Glucose values below 3.9 mmol/L or 70 mg/dL are rejected by the calculator.
Use cases
See how the tool fits into real work and everyday tasks.
If you already have clinician-set factors and a written meal calculation, enter the same values to see whether the carbohydrate term, correction term, and addition match your arithmetic. Follow the care plan's dosing and rounding instructions for any real decision.
A diabetes educator or learner can use clearly fictional values to see how grams per unit and glucose drop per unit appear in the equations. Treat the exercise as a lesson in the calculation, not a way to set personal factors.
When reviewing a recorded calculation, reproduce its unit, glucose values, meal carbohydrate, ICR, and ISF. This can help locate a mismatch in units or arithmetic; the page does not determine whether the plan or meal estimate was clinically appropriate.
Q&A
Find concise answers to common questions and confusing cases.
No. The unit selection changes the interpretation, not the entered values. The current glucose, target, and ISF fields are cleared when you switch; enter them again using the new unit consistently.
Current glucose, target glucose, ICR, and ISF must be valid numbers, and ICR and ISF must be above zero. The carbohydrate field may be blank, which the calculation treats as zero grams. Glucose below 70 mg/dL or 3.9 mmol/L also prevents a result.
The correction equation subtracts target glucose from current glucose. When current glucose is lower, that difference is negative and reduces the mathematical total. A negative correction is not low-glucose treatment guidance; low readings or symptoms call for your individual care instructions.
The calculator rounds the carbohydrate amount, correction, and total separately to one decimal place. The total uses the underlying unrounded amounts, so the displayed breakdown may differ from it by 0.1 U.
Notes
Review scope, result limitations, and important precautions before use.
The result is arithmetic based on entered values. It is not a prescription, diagnosis, or individualized medical recommendation. Use only settings and a target already established with your diabetes care team, and follow that plan for actual treatment decisions.
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