Due Date Calculator: How Many Weeks Pregnant Are You? (original) (raw)

How do I calculate my due date?

There are two main ways to calculate your due date:

The date of your last period

You can calculate your due date if you know the first day of your last menstrual period (LMP) before you got pregnant. Your due date is 40 weeks after the day you started your last period. This is the most reliable way to calculate your due date on your own at home, but it still isn’t perfect.

It works well because many people know the day they started their last period, either because they track it on an app or because they remember once they look at a calendar. But it might not always be accurate, especially if you have an irregular menstrual cycle or are on birth control.

How do I calculate my due date if I don’t know the date of my last period?

Don’t worry — not knowing the date of your last period doesn’t mean you won’t get a due date. Your pregnancy care provider will perform an ultrasound to determine how far along you are in your pregnancy and give you a due date. The due date your provider gives you is the most accurate.

The date you conceived (got pregnant)

If you know the exact day you conceived, you can use that information to figure out when your baby is due. Count ahead 38 weeks from the day you got pregnant. That day is your due date. This method is much harder to use and much less accurate because you must be 100% sure what day you got pregnant.

You may only know the specific day you got pregnant if you know when ovulation occurred. But even if you know when you ovulated, you still may not know exactly when pregnancy occurred. This is because sperm can live inside your body for up to five days and the entire process of releasing an egg lasts about 24 hours. It can be very hard to pinpoint the exact day the sperm and egg officially got together.

How do I calculate my due date if I had IVF?

If you did in vitro fertilization (IVF) to get pregnant, you can use your IVF transfer date to calculate your due date:

Like the other methods for calculating your due date, it’s always best to let your provider confirm your due date.

How accurate is a baby due date calculator?

A due date calculator is only an estimate. Your healthcare provider uses ultrasound to confirm your due date, typically at your first prenatal appointment. During an ultrasound, your provider measures the fetus. These measurements help your provider determine gestational age and confirm your due date. An ultrasound is the most reliable way to determine a baby’s due date.

Why is it important to calculate my due date?

It’s important to know your due date for planning purposes — knowing your expected delivery date helps you prepare to welcome your baby. You’ll have time to pack for the hospital and get the things you need for the baby, like a car seat. If you have other children, counting down the days until the new baby arrives can help siblings prepare for a new family member.

Knowing when you’re due also allows you to get appropriate prenatal care. This includes taking prenatal vitamins and getting prenatal screenings at the right times during your pregnancy. Your provider will also measure the fetus’s size and position throughout your pregnancy to ensure that it’s growing and developing as it should.

What is a reverse due date calculator?

A reverse due date calculator is helpful if you already know your due date and you want to find out when you got pregnant. To find out when you conceived, just subtract 266 days from your expected delivery date. You probably conceived around that day.