Pregnancy Due Date Calculator Pregnancy Due Date Calculator Based on your Last Menstrual Period (LMP) First day of your last period (LMP) JanuaryFebruary MarchApril MayJune JulyAugust SeptemberOctober NovemberDecember Average cycle length (Days) 28 Days (Average) Calculate Due Date Estimated Due Date - Week 0, Day 0 1st Trimester 2nd Trimester 3rd Trimester