Pregnancy Due Date Calculator - Find Out When Your Little One Arrives

Wondering when your due date is? Use our free baby due date calculator to find your estimated due date, your current week of pregnancy, and the trimester you're in. Just enter the first day of your last menstrual period, your conception date, or IVF transfer below to get started. 

Baby Due Date Calculator

Find your estimated due date.

First day of your last menstrual period (LMP)

Date of conception

Pregnancy is counted as 38 weeks from conception.

IVF embryo transfer date

Key Takeaways

  • Your due date is an estimate, not a deadline. Think of your due date as a "due month." Most pregnancies last approximately 280 days (40 weeks) from the first day of your last period. While only 5% of babies arrive on their exact date, having a target helps you prepare for the milestones ahead. It is perfectly normal to go into labor anywhere within a two-week window before or after that mark.

  • There are multiple ways to calculate your due date. Whether your provider uses your last period, the date of conception, IVF transfer date, or an early ultrasound, they will choose the most reliable method to help you plan for your new arrival.

  • Your due date can change and that's totally normal. If your first trimester ultrasound measurements don't match your LMP-based date, your doctor may adjust it. Early ultrasounds are actually the most precise way to confirm how far along you are.

  • Each trimester brings something new. From the early symptoms of the first trimester to the sweet spot of the second and the final preparations of the third, every stage of pregnancy is a chapter worth knowing about before it arrives.

  • Start preparing earlier than you think. By the third trimester, your to-do list fills up fast from choosing a pediatrician to packing your hospital bag. One thing many first-time moms don't realize is that most insurance plans cover a breast pump at no cost. You can order a pump before your baby arrives.

What is a Due Date?

According to the Cleveland Clinic, your due date is an estimate based on the standard 38-week (266-day) journey of fetal development. While your due date is a helpful estimate based on that timeline, remember that every pregnancy is unique. Your baby will arrive on their own schedule, influenced by many natural factors, so try to stay flexible as you wait for that special day!

How to Calculate Due Date  

While a typical pregnancy lasts about 280 days (40 weeks), very few babies arrive exactly on schedule. If you are wondering how to calculate your due date, your result is typically based on one of five methods: Your Last Period (LMP), Conception Date, IVF Transfer and by Ultrasound. Most healthcare providers use Naegele’s Rule to estimate your arrival date.

Method How It Works Accuracy
Last Period (LMP) 280 days from first day of last period Standard estimation
Conception Date 266 days from date of conception High (if date is known)
IVF Transfer Based on embryo age (Day 3 or Day 5) Extremely Precise
Ultrasound Measuring fetal "crown-rump length" Most accurate in 1st Trimester
Naegele’s Rule LMP + 7 days - 3 months Standard estimation

Last Menstrual Period (LMP)

This is the most common way to calculate your due date. Your healthcare provider counts 40 weeks forward from the first day of your last period. Even though conception typically happens about two weeks into your cycle, pregnancy is measured from the start of your LMP. That's why a full-term pregnancy is 40 weeks, even though the baby is technically only developing for about 38.

Conception Date

If you know exactly when you conceived, maybe you were tracking ovulation closely, you can count 38 weeks forward from that date. Keep in mind that sperm can survive in the body for up to five days, so pinpointing the exact moment of conception isn't always straightforward.

IVF Transfer Date

IVF pregnancies have the most precise due dates because the fertilization date is known. For a 3-day embryo transfer, add 263 days. For a 5-day (blastocyst) transfer, add 261 days.

Ultrasound Scan

If your cycles are irregular or you are unsure of your last period date, your OB or midwife will use an early ultrasound to measure your baby's size and estimate gestational age. First-trimester ultrasounds are actually the most accurate way to confirm a due date.

Naegele’s Rule

One of the most common ways to find your estimated due date is a method called Naegele’s Rule. This method is used by many providers. To calculate using Naegel’s Rule, take the first day of your last menstrual period (LMP), add seven days, and count back three months.

A Gentle Reminder

Due dates are estimates, not deadlines. Most babies arrive somewhere between 38 and 42 weeks. Your provider will guide you every step of the way.

What To Expect During Your Pregnancy

Once your pregnancy due date calculator result is in, you might find yourself asking: how many weeks pregnant am I? And what does that actually mean? Pregnancy is broken into three trimesters, each one a new chapter. Here's a look into what's ahead.

First Trimester: The Foundation (Weeks 1–13)

In the first 13 weeks, your body is doing more than you'd ever guess from the outside. Your baby goes from a tiny cluster of cells to a fully formed fetus with a heartbeat. Your hormones are shifting dramatically. That is what's behind the fatigue, nausea, and breast tenderness so many women feel early on. It's a lot, but it means everything is working exactly as it should.

Tip for this stage: This is the time to make your first prenatal appointment.

Second Trimester: The Golden Period (Weeks 14–27)

For a lot of moms, the second trimester is when pregnancy finally starts to feel enjoyable. The nausea tends to ease up, your energy comes back, and somewhere around weeks 16 to 22 you'll feel those first tiny movements. The baby’s gender is also revealed during this time (if you would like to know).

Tip for this stage: Your body is preparing for breastfeeding now. This is a great time to learn about different types of support. Many moms prefer wearable, hands-free options for their versatility.

Third Trimester: The Home Stretch (Weeks 28–40+)

The third trimester is equal parts exciting and exhausting. You might find yourself rearranging the nursery at midnight or suddenly obsessed with having everything ready. That nesting instinct is completely normal. So are the backaches, the heartburn, and walking into a room and forgetting why. You are almost there.

Tip for this stage: Your baby is practicing breathing. Now is the time to order your pump through insurance so it’s ready when they arrive.

First Trimester: Weeks 1–13

Welcome to the beginning of everything. The first trimester is when your body starts doing the incredible work of building a whole new person. You might not look pregnant yet, but a lot is happening and you'll probably feel it. Fatigue, nausea, and tender breasts are all signs that your hormones are hard at work.

What to expect from you and your baby:

  • Your baby's heart begins beating around week 6 
  • First prenatal appointment (usually around week 8) 
  • Nuchal translucency ultrasound and optional NIPT testing (weeks 10–13) 
  • Baby's major organs begin to form 
  • Morning sickness typically peaks and then starts to ease

What to focus on:

Start (or continue) a prenatal vitamin, stay hydrated, and be gentle with yourself. Rest when you need to. This is a big deal. You are growing a little human!

Second Trimester: Weeks 14 – 27

For many moms, the second trimester is when the exhaustion lifts, the nausea fades, pregnancy starts to feel more real and more exciting. Your bump becomes visible and you may feel the baby's first kicks (called quickening). There's a lot to look forward to during this trimester.

What to expect from you and your baby:

  • Morning sickness typically eases up by week 14–16 
  • You may feel baby's first movements (weeks 16–22) 
  • The anatomy scan ultrasound at 20 weeks 
  • Gender reveal, if you'd like to know 
  • Glucose screening for gestational diabetes (weeks 24–28) 

What to focus on:

Take advantage of your energy boost. This is a great time to set up your nursery, start a baby registry, research childcare, and think about your birth plan. And enjoy that bump; it's a beautiful thing!

Third Trimester: Weeks 28 – 40+

This is the final stretch and the most exciting one! Your baby is putting on weight, getting into position, and getting ready to meet you. You might feel more tired again, experience heartburn or back pain, and find yourself waking up at 3 a.m. to nest or overthink your hospital bag. All of that is completely normal. You are almost there.

What to expect from you and your baby:

  • Baby's lungs and brain continue maturing 
  • Group B strep test (weeks 36–37) 
  • Prenatal visits become weekly after week 36 
  • Braxton Hicks contractions become more noticeable 
  • Baby drops lower into your pelvis in the final weeks 

What to focus on:

Pack your hospital bag, choose a pediatrician, and start looking into your breast pump. Many insurance plans cover one at no cost, and it's one less thing to worry about after the baby arrives.

Frequently Asked Questions About Baby Due Dates

Can my due date change?

Yes. It is common for a doctor to adjust your due date after an initial ultrasound. If the baby’s size differs significantly from the date calculated by your last period, the ultrasound date is considered more accurate.

How accurate are due date calculators?

A due date calculator provides a highly reliable estimate, but it is rarely a guarantee. Research shows that only about 4% to 5% of babies are actually born on their exact due date. Instead of a single day, it is more helpful to view your due date as the center of a "five-week window."

What if I don't know my last period date?

Don'tworry. If your cycles are irregular or you simplydon'tremember the date, your healthcare provider will use an early-pregnancy ultrasound todeterminethe gestational age of the baby.

What if I don't know my last period date?

Don't worry. If your cycles are irregular or you simply don't remember the date, your healthcare provider will use an early-pregnancy ultrasound to determine the gestational age of the baby.

Does a due date calculator work for irregular cycles?

Yes, but it may be less accurate. Most calculators assume a 28-day cycle. If your cycle is consistently longer or shorter, a healthcare provider will likely rely on a first-trimester "dating ultrasound" to establish your official due date.

Is the due date calculated from conception or my last period?

Most medical professionals calculate your due date starting from the first day of your Last Menstrual Period (LMP). This is because most women don't know the exact date of conception, but they do remember when their last period started. This means you are technically "two weeks pregnant" before you even conceive.

What is the "Estimated Date of Delivery" (EDD)?

EDD is just the medical term for your due date. It is the date that spontaneous labor is expected to begin. Remember, it is an estimate; only about 4% of babies arrive exactly on their EDD.

What week does each trimester start and end?

The first trimester runs from week 1 to week 13. The second trimester spans weeks 14 through 27. The third trimester begins at week 28 and continues until birth, typically around week 40.

How many weeks is a full-term pregnancy?

A "full-term" pregnancy is officially between 39 weeks 0 days and 40 weeks 6 days. Babies born before 37 weeks are considered preterm.

When is the best time to start my baby registry?

Most parents start their registry during the middle of the second trimester (weeks 16–26). This gives you enough time to research essential gear and ensures that your items arrive before your baby shower or the third-trimester "nesting" phase begins.

When should I see a doctor after using a pregnancy due date calculator?

After using a pregnancy due date calculator, aim to schedule your first prenatal visit as soon as possible. Your provider will confirm your due date, check on baby's development, and set up your care plan. If you haven't already, now's the time to call your OB or midwife.

Mom using phone to search for breast pump insurance options while wearing wearable breast pumps

Did You Know Your Breast Pump May Be Covered by Insurance?

Most insurance plans are required to cover a breast pump at no cost to you. You can order yours before the baby even arrives. Check your insurance eligibility, connect with a covered supplier, and your pump will ship directly to your door.

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Medical Disclaimer

This due date calculator is for informational purposes only and isn't a substitute for medical advice. Since every pregnancy is a unique and wonderful journey, this estimated date is just a starting point. For the most accurate and personalized care, always stay in touch with your OB-GYN, midwife, or healthcare provider.

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