The use of standard all-in-one bags is increasingly widespread in patients of all ages across all care settings, in particular for pediatric patients. There are no tools, to our knowledge, that guides parenteral nutrition prescription from estimation of energy needs to the selection of the best fitting standard bag. We present a tool that helps the choice of the best standard bag based on the estimation of the patient's needs. The software considers: age, weight, sex, metabolic phase and type of venous access; energy and macro-micronutrient requirements. It contains a database of the compatible electrolyte and minerals that can be added to the PN bags. The software selects suitable PN bags, helping to reduce the time of PN prescription. The software limits or eliminates prescription or transcription errors while offering an evidence based prescription process. According to ESPEN/ESPGHAN guidelines, standard PN bags are suitable to most of the adult and paediatric patients. Using all-in-one standard bags in paediatric patients may be complex due to a wide range of patient ages and variable requirements. Several studies have shown that calculators are more accurate than traditional calculations. Using our tool, over and under feeding can be avoided and PN can be safe. The software is free and works on all fix and mobile devices.