Bolus Insulin Calculator
Calculate your total mealtime bolus: carbohydrate component (from ICR) plus blood glucose correction (from ISF and target). Does not model insulin on board — always account for IOB before dosing.
⚡ Bolus Estimator
Total Bolus Estimate
(Carbs ÷ ICR)
((BG − Target) ÷ ISF)
(IOB) — subtract manually
your IOB estimate
The Full Bolus Formula
The carb component covers the meal. The correction component (positive if BG is above target, negative if below) adjusts for current glucose level. IOB (insulin on board) is subtracted to prevent stacking — this calculator cannot model IOB automatically; you must estimate and subtract it manually or use a pump/bolus calculator that tracks it.
How a Mealtime Bolus Is Built
A mealtime bolus has two independent parts that this calculator adds together:
- Carbohydrate bolus — covers the food you are about to eat:
carbs ÷ ICR. With a 1:12 ratio, a 60 g meal needs 5 units. - Correction bolus — nudges an above- or below-target glucose back toward target:
(current BG − target) ÷ ISF. It is positive when you are high and negative when you are low, which is why a pre-meal low actually reduces your total bolus.
Because the two parts are calculated separately, you can see exactly how much insulin is for food versus for correction — useful when a total looks higher or lower than you expected.
Why IOB Isn't Included — and How to Handle It
This tool deliberately leaves insulin on board out of the automatic total, because a simple web form can't know when your last dose was. If you bolused within the past 3–4 hours, some of that insulin is still working, and adding a fresh correction on top of it is the classic cause of a post-meal low.
Estimate your active insulin with the Insulin on Board Calculator and subtract it, or use the IOB-aware Correction Dose Calculator for the correction portion. For a guided mealtime walkthrough, the Mealtime Insulin Dose Calculator covers the carb side step by step.
Frequently Asked Questions
What is a bolus insulin dose?
A bolus is the rapid-acting insulin you take at a meal or to correct a high reading, as opposed to basal (background) insulin. A mealtime bolus is the carbohydrate dose plus any correction dose.
How do I calculate my total bolus?
Add the carb bolus (carbs ÷ ICR) and the correction bolus ((current BG − target) ÷ ISF), then subtract any insulin on board. Example: 60 g ÷ 12 = 5 units, plus (180 − 100) ÷ 50 = 1.6 units, for about 6.6 units before IOB.
What is the difference between bolus and basal insulin?
Basal insulin provides steady background coverage over 24 hours; bolus insulin is taken in short bursts for meals and corrections. Most intensive regimens use both — see the Basal-Bolus Calculator.
Should a correction be included in my meal bolus?
Yes, if your blood glucose is above target before the meal — but always subtract insulin on board first to avoid stacking. If you are below target, the correction is negative and lowers the total bolus.
Source
- Walsh J, Roberts R. Pumping Insulin. 5th ed. 2012.
- American Diabetes Association. Standards of Care in Diabetes — 2024. Section 9.
Last reviewed: June 2025