Pregnancy Due Date Calculator

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About this calculator

The due date calculator uses the first day of your menstrual cycle and the average menstrual cycle length to provide three important pieces of information for dating your pregnancy:

• Probable ovulation date
• Fertility window (lmost likely period for conception, 5 days before and 2 days after your ovulation)
• Estimated due date (approximately 266 days from conception)

How ovulation and fertilization work

Around two weeks after your period, your body ovulates and your ovaries release one mature egg. The egg can be fertilized within 12 to 24 hours after it’s released, as it travels down the fallopian tube toward the uterus. If an egg meets up with a sperm cell that has made its way into the fallopian tube, it combines into one cell, a process that’s known as fertilization or conception. 

It takes about three to four days for the fertilized egg to move to the lining of your uterus, where it attaches or implants to the uterine wall. Once the embryo is implanted, the cells start to grow, eventually becoming the fetus and the placenta, which is tissue that can transport oxygen, nutrients and hormones from your blood to the developing fetus throughout pregnancy.

The Gestational period and your due date

The gestational period lasts approximately 266 days full term) from your conception date. It isn’t an exact date, but it is close. You may deliver a few days before or a few days after your calculated due date.

A normal pregnancy will take around 40 weeks, counting from the first day of your last menstrual period, which is about two weeks before conception actually occurs. Your pregnancy is divided into three trimesters. Each of these periods lasts between 12 and 13 weeks. During each trimester, changes take place in your body as well as in the developing fetus.