Calculate Your Conception Date: Expected Date Of Delivery

You’re pregnant! Now that you’ve received the wonderful news, one of the first questions you’ll want to know is “When is the baby due?” There are several key dates at the beginning of your pregnancy that can help you calculate your due date, including the first day of your last menstrual period and the date of conception. But sometimes at the beginning of pregnancy all of the timing seems a little bit confusing. So here’s a quick rundown on how the calculations are made.

It is not always easy to calculate when conception occurred, especially if the pregnancy was not planned. Women who have regular periods every 28 days have an easier time figuring out their conception dates, because they tend to ovulate around day 14 of their cycles. Women with irregular periods do not always know when ovulation occurs, making it harder to pinpoint the exact date of conception.

  • Mark your calendar when you start your period so you will have a reference point from which to start. Do this every month in order to record a pattern of how long your cycles are.
  • Listen to your body’s signals to know when ovulation is imminent. Some women feel an ache in their lower backs where the ovaries are and have increased cervical mucus during ovulation. Note the date of these signs on your calendar.
  • Use ovulation predictor kits to have a good idea when ovulation occurs. The surge of the LH hormone that you see on the dipstick (either a line or a digital readout) will alert you to this fact. If pregnancy occurs during this cycle, you will know it had to happen during one of the LH-surge days.
  • Visit one of the many pregnancy calculator websites that exist. When you plug in your due date, the computer can calculate your conception date by counting backwards. The calculators tend to base their dates on a 28-day cycle, so it may be slightly off if your cycles are longer or shorter.
  • Have an ultrasound done to measure the age of your baby. As early as 5 weeks, ultrasounds can accurately date a pregnancy and allow you to calculate the date of conception. Ultrasounds are especially helpful if you do not keep track of your periods and have an unplanned pregnancy.

Alternatively, if you already have the due date and you’re looking to pinpoint the date of conception (did it happen on that romantic getaway weekend?), you can use an online conception calculator, or you can take your due date and subtract 266 days. That reflects a total of 280 days for the pregnancy, minus 14 days for the first two weeks before you ovulated and conceived. Got that? Good, because now it’s time to focus on what’s really important – the healthy development of your new little one.