Precise dosing of insulin at meals and for correction of glycemia is crucial for sustention of optimal blood glucose concentration. Modern insulin delivery systems (such as insulin pumps) not only provide high dosing precision, but are also capable of calculating necessary dose by means of built-in software – so called “bolus calculators”. However, patient-oriented approach to “calculator” settings, as well as their timely correction is imperative for attainment of desired precision. Though similar in their principle, various “calculators” also feature essential peculiarities that have to be considered for optimal adjustment. The review addresses current evidence for “bolus calculator” efficiency, comparative analysis of these applications and description of their key distinctions.