When you get your first positive pregnancy test, one of the lingering questions you might have is when you actually become pregnant. To calculate the exact date of pregnancy, also known as the date of conception, you must first understand your menstrual cycle. Armed with a calendar, you can count backward to find out the most likely date of pregnancy, and reconcile that date with your own memories of when you may have had intercourse during that time.
Step 1
Count how many days long your cycle is. Your cycle lasts from the first day of your last period to the first day of your next period. The average length of a woman's menstrual cycle is 28 days, according to WomensHealth.gov. Some women may have longer or shorter periods, so it's important to keep track of the first day of each period by marking on a calendar when it begins. Count the days in between, including the marked days, to get the cycle length.
Step 2
Locate the date of ovulation on your calendar. Ovulation typically happens halfway through a woman's cycle. If you have a 28-day cycle, then you'll likely ovulate on day 14, notes the BabyMed website. Mark day 14 on your calendar as the date of ovulation by counting back 14 days from the date your period should have started, or counting forward 14 days from the last period you had.
Step 3
Ask your partner if he remembers, or search your own memory as to when you had intercourse closest to the date of ovulation. Ovulation lasts anywhere from two to five days, so as long as you had intercourse somewhere in the five-day period after ovulation, it's likely the exact date of pregnancy.
Tips and Warnings
- Use your conception date when you calculate your due date. Your OB/GYN will want the date of your last period to calculate your due date and schedule appointments, ultrasounds and other tests throughout your pregnancy.
Things You'll Need
- Calendar
- Pen
