While it’s true that most pregnancies last 40 weeks, there are other factors at play which will determine your due date. For example, both menstrual and ovulation periods count as the first two weeks of pregnancy. Unless you can pinpoint exactly what point of your ovulation cycle you were in at the time of fertilization, it’s difficult to know how far along you are and what date you’ll meet your baby. Our due date calculator can help. Using both the date of your last period and the length of your regular cycle, or exact date of conception, our due date calculator will quickly work out your estimated due date.