Pregnancy calculator software used by real doctors and nurses - Pregtool. Use Pregtool to calculate the EDD (End Due Date or Delivery Date) and GA (Gestational Age) from the entered: 1.LMP (Last Menstrual Period) or US (date of UltraSound). 2.GA in US (Gestational Age in UltraSound), at least 4 weeks and not more than 40 weeks - this software would imply the non-wwd format input according to this rule.