Estimate your due date from your last period, an ultrasound, the date of conception or an IVF transfer, and see how far along you are.
A full pregnancy lasts about 40 weeks, or 280 days, counted from the first day of the last menstrual period. Adding 280 days to that date gives the standard due date. It is only an estimate: just a small share of babies arrive on the due date, and most are born within a couple of weeks either side. A due date is best seen as the middle of a range, and a baby born between 37 and 42 weeks is considered full term.
If your cycle is longer or shorter than 28 days, ovulation shifts with it, so the due date moves by the same number of days. If you know the date of conception, the due date is 266 days after it. An ultrasound gives the age of the pregnancy on the day of the scan, and the due date follows from that. For IVF, the embryo’s age on the transfer date is taken into account, so a day 5 embryo has about 261 days to go from the transfer. Early ultrasounds are usually the most accurate way to date a pregnancy.
The results show your due date, how far along you are in weeks and days, your trimester, the likely date of conception, and the typical size of a baby at this stage. The table lists each pregnancy week with its dates, the trimester it falls in, and a few milestones. Your own doctor or midwife may change the due date after an ultrasound or as the pregnancy goes on.
It is 280 days after the first day of your last period, which is 40 weeks. If your cycle is not 28 days long, the date moves by the difference.
Only about 4% of babies are born on the due date. Most arrive within about two weeks before or after it.
Add 266 days to the date of conception. This is 38 weeks, since conception happens about two weeks after the start of the last period.
The calculator counts back from the embryo transfer using the age of the embryo. A day 3 embryo adds 263 days to the transfer date, a day 5 embryo adds 261 days, and a day 6 embryo adds 260 days.
The second trimester starts after 12 weeks of pregnancy, and the third trimester after 27 weeks. A baby is considered full term from 37 weeks.
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