First day of your last period The most common way to calculate your pregnancy due date is by counting 40 weeks from the first day of your last menstrual period (LMP). And thats how most healthcare providers do it.

How can I calculate my due date easily?

Most pregnancies last around 40 weeks (or 38 weeks from conception), so typically the best way to estimate your due date is to count 40 weeks, or 280 days, from the first day of your last menstrual period (LMP). Another way to do it is to subtract three months from the first day of your last period and add seven days.

How do you determine how many weeks pregnant your baby is?

Add 280 days (40 weeks) to the first day of your last menstrual period (assuming a 28-day cycle). Your menstrual period and ovulation are counted as the first two weeks of pregnancy.

What is my due date without knowing my last period?

What if I dont know the date of my last menstrual period?If you know you had your LMP during a particular week, your doctor can estimate your due date accordingly.If you have no idea when your last period was, your doctor may order an ultrasound to determine your due date.