Introduction
The Due Date Calculator helps you figure out when your baby is likely to be born. Most pregnancies last about 40 weeks, or 280 days, from the first day of your last menstrual period. By entering this date, our calculator estimates your expected due date so you can plan ahead and track your pregnancy week by week. Keep in mind that only about 5% of babies arrive on their exact due date. Most babies are born within a two-week window before or after. Your doctor or midwife may adjust your due date based on ultrasound results or other factors. This tool gives you a helpful starting point to understand your pregnancy timeline.
How to Use Our Due Date Calculator
Enter details about your pregnancy using one of four methods, and this calculator will estimate your due date, show your current gestational age, and display key milestones throughout your pregnancy.
Calculation Method: Choose how you want to calculate your due date. You can pick from Last Menstrual Period (LMP), Conception Date, IVF Transfer Date, or Ultrasound Date. The fields below will change based on your choice.
First Day of Last Period: If using the LMP method, enter the first day of your most recent menstrual period. This is the most common way doctors estimate a due date.
Average Cycle Length: Enter the typical number of days in your menstrual cycle. The standard is 28 days. If your cycle is longer or shorter, the calculator adjusts your due date to account for the difference.
Conception Date: If you know the exact date you conceived, select the Conception Date method and enter that date. The calculator adds 266 days to find your due date.
Embryo Transfer Date: If you used IVF, select the IVF Transfer Date method and enter the date your embryo was transferred.
Transfer Type: Choose whether your IVF transfer was a Day 3 or Day 5 embryo. A Day 3 transfer adds 263 days and a Day 5 transfer adds 261 days to calculate your due date.
Ultrasound Date: If using the Ultrasound method, enter the date your ultrasound was performed. Ultrasounds done in the first trimester (before 13 weeks) give the most accurate results.
Gestational Age at Ultrasound: Enter the number of weeks and days your doctor said the baby measured at your ultrasound. The calculator uses this age along with the ultrasound date to work backward and find your due date.
Once you have filled in your information, click Calculate Due Date to see your estimated due date, a countdown of days remaining, trimester progress, key pregnancy dates, milestones, and a week-by-week timeline. Click Reset to clear your entries and start over.
How to Calculate Your Due Date
A due date calculator estimates the day your baby is most likely to be born. Most pregnancies last about 40 weeks, or 280 days, counted from the first day of your last menstrual period (LMP). This date is also called the estimated date of delivery (EDD). Knowing your due date helps you and your doctor plan prenatal care, schedule important tests, and prepare for your baby's arrival. You can also use our Days Until Calculator to count down to your due date, or the Date Duration Calculator to measure exactly how many days remain between any two pregnancy milestones.
Methods Used to Calculate a Due Date
There are several ways to figure out when your baby is due. The most common method uses the first day of your last menstrual period (LMP). The calculator adds 280 days to that date, then adjusts if your cycle is longer or shorter than the standard 28 days. For example, if your cycle is 32 days, your due date shifts forward by 4 days because ovulation likely happened later.
If you know your conception date, the calculation adds 266 days from that day instead. This works well for people who tracked ovulation closely. For those who used in vitro fertilization (IVF), the due date is based on the embryo transfer date. A Day 3 embryo transfer adds 263 days, while a Day 5 blastocyst transfer adds 261 days, since the embryo is two days more developed.
An ultrasound can also be used to estimate your due date. Your doctor measures the baby's size and tells you the gestational age in weeks and days. The calculator uses this information to work backward and find when your pregnancy started, then counts forward to 40 weeks. First-trimester ultrasounds (before 13 weeks) give the most accurate results.
What the Trimesters Mean
Pregnancy is divided into three trimesters. The first trimester covers weeks 1 through 12. During this time, the baby's organs begin to form, and many women experience morning sickness and fatigue. The second trimester spans weeks 13 through 27. Most women feel more energetic, and the baby grows quickly — this is when you usually find out the baby's sex during an anatomy scan around weeks 18 to 22. The third trimester runs from week 28 until birth. The baby gains weight rapidly, and doctor visits become more frequent.
Key Pregnancy Milestones
Several important milestones happen throughout pregnancy. Around week 5, the baby's heartbeat can be detected. At week 12, the risk of miscarriage drops significantly. Week 20 marks the halfway point. Week 24 is known as the viability milestone, meaning the baby has a chance of surviving if born early. By week 37, the baby is considered full term and is generally ready for life outside the womb.
How Accurate Is a Due Date?
A due date is an estimate, not a guarantee. Only about 5% of babies are born on their exact due date. Most babies arrive within a window of two weeks before or after the estimated date. A baby born between 37 and 42 weeks is considered to have arrived at a normal time. Your doctor may adjust your due date based on early ultrasound measurements, especially if they differ from the LMP-based estimate by more than a week. Our Age Calculator can be useful after birth to track your baby's exact age in weeks, months, and years.
Important Things to Keep in Mind
This calculator provides an estimate for educational purposes only. It does not replace medical advice. Always confirm your due date with your healthcare provider, who can use physical exams and ultrasound measurements for the most accurate assessment. If your menstrual cycle is irregular, or if you are unsure about dates, an early ultrasound is the best way to determine gestational age. Talk to your doctor about your specific prenatal care schedule, recommended screenings, and any concerns you may have throughout your pregnancy. During pregnancy, staying on top of your nutrition is important — tools like our Macro Calculator, Protein Calculator, and Water Intake Calculator can help you meet the increased nutritional demands of each trimester. You may also want to use our Ideal Body Weight Calculator or Waist to Hip Ratio Calculator to establish a baseline before pregnancy, and a Sleep Calculator to ensure you're getting enough rest as your body works harder to support your growing baby. Prioritizing safe caffeine limits is also a common concern during pregnancy that is worth discussing with your provider.