Pregnancy Due Date Calculator
Calculate your estimated due date using medically recognized methods and track your pregnancy journey with milestones, baby size comparisons, and more
Select the first day of your most recent menstrual period
Most women have a 28-day cycle (22-44 days range). Adjust if yours differs.
Calculate Your Due Date
Select a calculation method and enter your dates to see your estimated due date, pregnancy progress, milestones, and more.
How to Use the Pregnancy Due Date Calculator
Choose Your Calculation Method
Select from four medically recognized methods: Last Menstrual Period (most common), Conception Date (if you know when conception occurred), Ultrasound (using measurements from an ultrasound scan), or IVF Transfer Date (for in vitro fertilization pregnancies). You can also use the Reverse mode to plan a conception date around a desired due date.
Enter Your Dates and Details
For the LMP method, enter the first day of your last period and adjust your average cycle length if it differs from 28 days. For Conception Date, enter the date you believe conception occurred. For Ultrasound, enter the scan date and measured gestational age. For IVF, enter your transfer date and select the embryo age (Day 3, Day 5, or Day 6).
Calculate and Review Your Results
Click Calculate Due Date to see your estimated due date prominently displayed, along with your current gestational age, trimester, days remaining, and the likely delivery window (37-42 weeks). Scroll down to see your pregnancy progress chart, baby size comparison, and milestones timeline.
Explore Additional Details
Review the trimester dates, key prenatal appointments, your baby's predicted zodiac sign and birthstone, and the full pregnancy milestones timeline. You can export your results to CSV or print them to share with your healthcare provider. Remember that due dates are estimates, and always consult your doctor.
Frequently Asked Questions
How accurate is a pregnancy due date calculator?
Pregnancy due date calculators provide a good estimate, but only about 5% of babies are born on their exact estimated due date. Most babies arrive within a two-week window around the due date, with the majority born between 37 and 42 weeks of gestation. The accuracy depends on the calculation method used. Ultrasound dating in the first trimester is considered the most accurate, typically within 5-7 days of the actual delivery date. The LMP method using Naegele's Rule assumes a regular 28-day cycle, so accuracy improves when you adjust for your actual cycle length. IVF dates are extremely precise since the exact fertilization timing is known. Your healthcare provider may adjust your due date based on ultrasound measurements taken during your first prenatal visit.
What is Naegele's Rule and how does it calculate my due date?
Naegele's Rule is the standard formula used by healthcare providers to estimate a pregnancy due date. It works by adding 280 days (40 weeks) to the first day of your last menstrual period (LMP). This assumes that conception occurs approximately 14 days after the start of your period, based on a 28-day menstrual cycle. If your cycle length differs from 28 days, the formula is adjusted by adding or subtracting the difference. For example, if you have a 32-day cycle, 4 extra days are added to the standard 280 days. While simple and widely used, Naegele's Rule has limitations because it assumes regular cycles and a consistent 14-day follicular phase. Your doctor may use ultrasound dating to refine the estimate if needed.
Can my due date change during pregnancy?
Yes, your due date can change, and this is relatively common. The most frequent reason for a due date change is when an early ultrasound measurement differs significantly from the date calculated using your last menstrual period. If the ultrasound estimate differs by more than 7 days in the first trimester or more than 10-14 days in the second trimester, your healthcare provider may adjust your due date to match the ultrasound measurements. Other factors that may lead to a due date change include irregular menstrual cycles that made the initial LMP calculation less reliable, or if you were unsure about the exact date of your last period. Once a due date is established by a first-trimester ultrasound, it typically remains unchanged for the rest of the pregnancy.
What is the difference between gestational age and fetal age?
Gestational age and fetal age are two different ways to measure how far along a pregnancy is. Gestational age is counted from the first day of the last menstrual period (LMP), which is about two weeks before conception actually occurs. This means gestational age is always approximately two weeks more than the actual age of the embryo or fetus. Fetal age (also called embryonic age or conceptional age) counts from the actual date of fertilization. So when your doctor says you are 10 weeks pregnant, that is the gestational age, and the fetus is actually about 8 weeks old. Most pregnancy timelines, due date calculations, and prenatal care schedules use gestational age as the standard measurement. The 40-week pregnancy duration refers to gestational age.
What does full-term pregnancy mean and when is it safe to deliver?
The American College of Obstetricians and Gynecologists (ACOG) defines pregnancy terms as follows: Early term is 37 weeks through 38 weeks and 6 days, full term is 39 weeks through 40 weeks and 6 days, late term is 41 weeks through 41 weeks and 6 days, and post-term is 42 weeks and beyond. A baby born at full term (39+ weeks) has had the optimal time for brain, lung, and liver development. While babies born at 37-38 weeks are generally healthy, research shows that waiting until at least 39 weeks reduces risks of breathing problems, feeding difficulties, and NICU admissions. Delivery is not typically induced before 39 weeks unless there are medical complications. Your healthcare provider will monitor your pregnancy closely as you approach and pass your due date.
How is the due date calculated for IVF pregnancies?
IVF (in vitro fertilization) due dates are calculated differently because the exact timing of fertilization is known. For IVF pregnancies, the calculation starts from the embryo transfer date and adds the number of days to reach a full 280-day (40-week) gestational period, minus the embryo's age at transfer plus 14 days. For a Day 3 embryo transfer, the due date is the transfer date plus 263 days. For a Day 5 blastocyst transfer, it is the transfer date plus 261 days. For a Day 6 transfer, it is 260 days. The logic is that a Day 3 embryo has a gestational age of 17 days at transfer (3 days embryo age plus 14 days from theoretical LMP to ovulation), so 280 minus 17 equals 263 days remaining. IVF dating is considered the most accurate method since the exact fertilization date is known.