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Pregnancy Due Date Calculator: How Far Along Am I?

Finding out that you’re pregnant is exciting news and the beginning of a life-long journey. But like any other life-altering event, it requires careful preparation and planning. And the best way to start is by calculating your due date to know when you’ll see your baby. In this article, you’ll learn more about finding out your due date, how it’s measured, and how to calculate it using different techniques.

Pregnancy Due Date Calculator - Visual representation of a tool providing estimated due dates based on pregnancy information.
Calculation method

You just did a pregnancy test and found out that you’re pregnant. Congratulations! You’re probably full of excitement and have many questions. One of the first things you might want to find out is when you will meet your new baby. Our easy-to-use pregnancy due date calculator can be a great way to prepare for the due date and plan your pregnancy and prenatal care better.

Using the due date calculator

The WomanLog free pregnancy due date calculator uses the first day of your last menstrual period, your date of conception if you happen to know it, or your IVF transfer date to calculate how far along you are in your pregnancy and estimate a due date for your baby. Your obstetrician will also want this information to ensure your prenatal care is on track. If you’re still planning to conceive, knowing your due date can help you plan your life and pregnancy accordingly.


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Are you pregnant?

For most people, the first sign of pregnancy is a missed period, but the egg will have been fertilized a few weeks earlier at ovulation—around the mid-point of your cycle.

Other early signs of pregnancy—such as tender breasts, darkening areolas, cramping, spotting, fatigue, bloating, mood swings, frequent urination, heightened sense of smell, and nausea or morning sickness—appear over the next three to four weeks after that first missed period.

An at-home pregnancy test can confirm pregnancy as early as 10 days after fertilization. However, testing after the first day of your missed period can help you avoid a false negative. Pregnancy can also be confirmed by a laboratory blood test, which is slightly more sensitive than an at-home urine test.

When are you due?

Pregnancy typically lasts 40 weeks—or 280 days from the first day of your last period. It’s divided into three trimesters to help track the development of your pregnancy:

  • first trimester—weeks 1 to 12
  • second trimester—weeks 13 to 28
  • third trimester—weeks 29 to 40

A full-term pregnancy—one in which the baby has all the time it needs to fully develop and have the best possible start in life—is 39 to 40 weeks. However, plenty of babies arrive a little early or a little late.

A baby born before week 37 is considered premature or preterm. Babies born between weeks 29 and 33 are moderately preterm, while babies born between weeks 23 and 28 weeks are extremely preterm. The last few weeks of pregnancy are crucial for organ development. This is why preterm babies have a greater chance of breathing problems, low blood sugar, and other health issues.

A pregnancy that exceeds 40 weeks is considered late-term, and one that goes past week 42 is post-term. However, first pregnancies tend to be slightly longer, and it is not uncommon for labour to start in week 41. With late-term pregnancies there is a greater risk of prolonged labour, infection, birth trauma, and other problems for the baby and mother.

Visual guide to 'Estimated Due Date in Pregnancy - Exploring the calculation and significance of the anticipated arrival date for expecting mothers

What is an estimated due date during pregnancy?

An estimated due date (EDD) is the date when the baby growing in your uterus is expected to be fully developed and you will spontaneously go into labour. Fewer than 5% of babies are born on their estimated due date, but more than 90% are born within two weeks either side of the EDD.

First, it’s necessary to understand how a due date is calculated to know how far along your pregnancy is. There are several ways used to measure a due date—such as by tracking a gestational age, applying Naegele’s rule,  measuring a fetal age, and using an ultrasound.

Gestational age

Gestational age is calculated from the first day of your last menstrual period (LMP). While technically, you only become pregnant mid-cycle when an egg released at ovulation is fertilized by sperm, your body began preparing for the pregnancy with your last period. The average pregnancy lasts 280 days counting from LMP.

Naegele’s rule

Franz Naegele was a German obstetrician who published a book for midwives in 1830. He developed a simple method to help the midwives predict approximately when a pregnant woman would go into labour. To calculate your estimated due date, start with the first day of your last period, count back three months, add seven days, and then add a year.

Fetal age

Fetal age is counted from the moment of conception when the egg is fertilized and begins to develop. This is the actual age of your baby—about two weeks behind gestational age. Most women don’t know when they ovulate, so fetal age is usually estimated by comparing certain measurements against gestational age.

Ultrasound Scan

Ultrasound or sonogram imaging uses high-frequency sound waves to give your doctor a picture what’s happening inside your body. All babies progress through the same developmental stages, but there is some variation according to genetics and environment. Your OB/GYN will likely do an ultrasound scan towards the end of your first trimester.

As Naegele’s rule assumes standard parameters that don’t apply to all women, your doctor will use the LMP-based estimate of gestational age, detailed information about your menstrual and health history, and ultrasound-based estimates to provide the best possible prenatal care.

The most consistent growth rates occur between weeks 8 and 12. During this window, measurements for crown-rump length, head circumference, femur length, and other parameters allow a trained specialist to estimate gestational age accurately within 5 days. As pregnancy progresses, there is greater variation in how each fetus develops, so while scans done in the second and third trimesters provide important and useful information, they are slightly less accurate for predicting your due date.

Planning Pregnancy Due Date' - Visual guide addressing considerations and factors for those exploring the possibility of planning their due date

Can I plan my due date?

If you are pregnant, your baby is already on its own schedule. All you can do now is follow along with the stages of development and take steps to support your health and wellbeing. A pregnancy due date calculator is a helpful tool that lets you know when to expect your baby and how far along you are in your pregnancy. However, if you are still in the planning stages, you can use our due date calculator to help you decide on your next steps.

Family health organizations often recommend that prospective parents consciously plan for pregnancy, so they have the best chance to prepare. When you have a good idea of what to expect and when, you can develop habits that support pregnancy, avoid harmful substances and activities that might stress a developing fetus, and get early prenatal care. Some studies suggest that planned pregnancies are more likely to result in healthy babies.

However, even with the best of intentions, sex and conception happen organically and are not entirely predictable. Focussing too much on scheduling a pregnancy can sometimes be counterproductive. It takes most couples at least one year to conceive, and less than 30% of people actively trying to get pregnant manage to conceive in the first cycle. Don’t worry if it doesn’t happen right away. See your doctor for a check-up and find out what you can do to enhance your health, facilitate conception, and ensure your future pregnancy goes smoothly.

Can my due date change?

An estimated due date can fluctuate depending on the method used, the accuracy of the information provided, and how closely your unique pregnancy tracks with average parameters. Reasons an estimated due date might be adjusted include not knowing the date of your last period, variations in the baby’s growth rate, and the possibility of multiple fetuses.

  • Irregular cycles: If your cycle is irregular, determining precisely when ovulation happens is more difficult.

In an average 28-day cycle ovulation occurs mid-cycle, around day 14, but this is not the case for everyone. A “normal” cycle can last anywhere from 21 to 35 days. So, even knowing the precise date when your last period started won’t necessarily let you pinpoint the date of ovulation. Tracking your period over time is the best way to get to know your cycle.

But to be sure you remember the time of your last period, we recommend you use a period tracker or calculator. WomanLog offers a free version of a period calculator to track your monthly symptoms and predict fertile days and menstruation.

  • Late first ultrasound: Normally, an initial ultrasound is performed towards the end of the first trimester to confirm the heartbeat, determine the size of the fetus, and find out if you’re expecting twins or multiples. Fetal measurements taken between weeks 8 and 12 are most accurate for predicting the due date. If you don’t realize you’re pregnant right away, or it takes longer to schedule an ultrasound for some reason, the estimated due date for your baby may be slightly less accurate.
  • Your fundal height is above or below average: Fundal height is the distance between the pubic bone and the top of the uterus. This measurement is another common tool for estimating how far along you are in your pregnancy. Fundal height generally tracks with the standard growth chart according to estimated gestational age. If your uterus is smaller or larger than the average range, it could throw off the estimated gestational age by a few weeks.

How to work out my pregnancy due date with irregular periods

Around 25% of reproductive-age women have irregular periods. While this can make it trickier to determine a starting date for gestational age, ultrasound scans and growth charts help narrow the range of uncertainty. And remember, your baby’s development is not correlated to your menstrual cycle, regular or irregular. Once that egg is fertilized and the embryo successfully embeds itself in the uterine wall, your baby has its own timeline for development.

How to calculate the due date if you’ve had IVF?

When you conceive through in vitro fertilization (IVF), your due date is calculated using the IVF transfer date. Most embryo transfers take place three to five days after egg retrieval and fertilization. To get your estimated due date, add 266 days (38 weeks) to the embryo transfer date. The good news is that with IVF, estimated due dates are much more accurate because your doctor knows exactly when the embryo is implanted in the uterus.

Calculate your due date with the WomanLog due date calculator

Pregnancy is an exciting journey, and we want to make it as easy as possible for you. Knowing when to expect your baby can give you peace of mind. The WomanLog pregnancy due date calculator uses gestational age, your IVF transfer date, or the date of conception if you happen to know it, to give you an approximate birth date for your baby. This is a free tool you can use at any time to track how far along you are in your pregnancy. For more insight into each stage of pregnancy, we recommend our free pregnancy tracking app to help you keep an eye on your progress and track daily changes. Ease your pregnancy journey with WomanLog!

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