How Do I Know How Much Months Pregnant I Am

Due Date Calculator

When is your baby due? Use this pregnancy calculator to find your due date based on the date of your last menstrual period, conception date, IVF 3-day or 5-day transfer date or date of your last ultrasound.

Medically Reviewed by Aaron Styer, M.D.

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on July 6, 2021

First day of last period

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. So if your last period started on April 11, you'd count back three months to January 11 and then add seven days, which means your due date would be January 18.

This is how your doctor will estimate your due date — and it's a pretty solid target. But remember: It's just as normal to deliver a week or two before or after.

Conception date

Calculating your due date based on the first day of your last period works well for women who have a relatively regular menstrual cycle. But if your cycle is irregular, the LMP method may not work for you.

Because a reliable estimated date of delivery (EDD) is important, you and your practitioner can use your conception date instead if you remember it. Just add 266 days to get your estimated due date.

IVF transfer date

There are more than 250,000 assisted reproductive technology cycles performed each year in the United States, resulting in about 77,000 or more babies born a year, according to the Centers for Disease Control and Prevention (CDC).

If you are part of the growing tribe of in vitro fertilization (IVF) moms, you can calculate your due date more precisely using your IVF transfer date.

Ultrasound scan

Even if you can't pinpoint when you conceived, forget the day of your last menstrual period or aren't sure when ovulation occurred, other clues can help you and your practitioner determine your due date at your first prenatal appointment, including:

An early ultrasound, which can more accurately date the pregnancy. Just be aware, however, that not all women get an early ultrasound. Some practitioners perform them routinely, but others only recommend one if your periods are irregular, you're 35 or older, you have a history of miscarriages or pregnancy complications, or the due date can't be determined based on your physical exam and LMP.
Pregnancy milestones such as the first time the baby's heartbeat is heard (around week 9 or 10, though it can vary) and when you first feel fetal movement (on average between 18 and 22 weeks, but it can be earlier or later), can give clues as to whether your due date is accurate.
Your fundal height, which is the measurement from your pubic bone to the top of your uterus, is checked by your practitioner at each prenatal visit and helps confirm your due date.
The size of your uterus, which will be noted when your initial internal pregnancy exam is performed, can also be a factor in pinpointing the EDD.

Can I plan my due date?

Whether you're trying to avoid being very pregnant in the middle of summer or are a teacher who wants to maximize time off with your little one, you can try to time when you conceive in order to "plan" your due date. But even if you're one of the lucky ones who's able to get pregnant when she really wants to, just remember that you probably won't be able to map out exactly when you'll give birth to the day (or even the week or month!).

Still, you can try our Ovulation Calculator, which uses the date of your last menstrual period and your typical cycle length to discover the days you're most likely to be fertile and increase your chances of conceiving.

Can my due date change?

Yes, your due date can change. While it's definitely not a reason to worry, your doctor may change your due date for a number of reasons as your pregnancy progresses.

It may be that you have irregular periods and your early ultrasound dating was off, or that your first ultrasound was in the second trimester.

It could also be because your fundal height is abnormal, or your levels of alpha-fetoprotein (AFP), a protein made by the baby, are outside the usual range. Talk to your practitioner if you have any questions or concerns.

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What to Expect Before You're Expecting, 2nd edition, Heidi Murkoff.

WhatToExpect.com, Pregnancy Week-by-Week, 2020.

WhatToExpect.com, 7 Signs of Ovulation, June 2019.

WhatToExpect.com, When and Why Your Doctor May Change Your Due Date, September 2018.

WhatToExpect.com, How Many Weeks, Months and Trimesters in a Pregnancy?, September 2018.

WhatToExpect.com, In Vitro Fertilization (IVF), April 2020.

WhatToExpect.com, Birth Symbols by Month: Zodiac, Birthstone, Flower and Tree, September 2018.

American College of Obstetricians and Gynecologists, Methods for Estimating the Due Date, May 2017.

Centers for Disease Control and Prevention, ART Success Rates, March 2020.

March of Dimes, Calculating Your Due Date, 2020.

Stanford Children's Health, Calculating a Due Date, 2020.

Princeton IVF, Due Date Calculator for Fertility Patients, 2014-2019.

Mayo Clinic, Prenatal Care: First Trimester Visits, November 2018.

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