Pregnancy Due Date and Week Calculator

Estimate pregnancy week and due date

Start with the last period

Pregnancy length is traditionally counted from the first day of the last menstrual period. Week 0+0 therefore begins about two weeks before typical conception. Enter that date and choose the date for which you want the calculation. The calculator adds 280 days, or 40 weeks, and reports completed weeks plus remaining days.

Reading the week notation

A result of 12+3 means twelve complete weeks and three days. In everyday speech this is often called week 13 because the thirteenth week has started. Swedish healthcare uses the same convention: 1177 describes “pregnant in week 13” as 12+0 through 12+6. The conception date shown here is simply 14 days after the period began and can be quite uncertain.

A due date is an estimate

The date supports planning; it is not an appointment for birth. 1177 says pregnancy commonly lasts from 37 to 42 weeks. Ovulation can occur earlier or later than the standard assumption, especially with irregular cycles, and bleeding interpreted as a period may have another explanation. The estimate can therefore differ from the date used by maternity care.

Prefer clinical dating

Ultrasound can show how long pregnancy has progressed and is used for dating. Once a midwife or scan confirms a due date, use that date instead of this preliminary calculation. This tool cannot assess development, pain, bleeding, or other symptoms. Contact a midwife or 1177 for Swedish healthcare advice and seek urgent care according to their guidance.