Due date calculator

The due date is counted from the first day of your last period, taking your cycle length into account.

The tool offers four methods:

• last period: 280 days (40 weeks) are added to the first day of the last period, taking your cycle length into account;
• conception date: 266 days (38 weeks) are added to the date of conception or ovulation;
• embryo transfer (IVF): we start from the transfer date and the age of the embryo (3 or 5 days); this is the most reliable method after IVF;
• ultrasound: from the age measured on a given date, the due date is calculated.

Results may differ by a few days depending on the method.

From the calculated date, the tool places the usual main stages of follow-up: first-trimester ultrasound, anomaly scan, gestational diabetes screening, growth scan, start of term. These are indicative windows: your doctor sets the schedule suited to your pregnancy.

The date calculated from the last period assumes a regular cycle and ovulation around mid-cycle. If your cycles are irregular or you do not remember the date of your period, the first-trimester ultrasound gives the most accurate dating. The doctor may then adjust the due date.

Only 4 to 5% of babies are born exactly on the due date. Birth is considered at term between 37 and 41 weeks + 6 days, hence the display of a term window. Regular follow-up allows the end of pregnancy to be monitored.

Few babies are born exactly on the due date: birth most often happens around it. Ultrasound dates the pregnancy more precisely.