If you were 20 weeks and 4 days on April 13th when did conceive?

To calculate when you conceived, subtract the number of weeks and days from your due date. The average pregnancy lasts 40 weeks, so you would subtract 20 weeks and 4 days from your due date to find your estimated date of conception.

Your due date would be October 20th. Subtracting 20 weeks and 4 days from October 20th, we get June 27th. Therefore, you conceived around June 27th.