Pregnancy Due Date Calculator — Find Your Estimated Delivery Date
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Pregnancy Due Date Calculator — Find Your Estimated Delivery Date
Estimate your due date, current pregnancy week, trimester and baby milestones using your last menstrual period, conception date, IVF transfer date or an ultrasound measurement.
Pregnancy Details
Your saved calculations will appear here.
Wk 1–13
Wk 14–27
Wk 28–40
Enter your dates above to see this week's milestone.
Complete Guide
Understanding Your Pregnancy Due Date: A Complete Guide
Few numbers are anticipated as intensely as a pregnancy due date, yet it is worth understanding from the very start that this date is an estimate, not a prediction with a fixed outcome. Only a small share of babies are actually born on their exact estimated due date; most arrive within a window of about two weeks either side of it. What the due date really gives you is a reliable planning anchor — a way to schedule prenatal visits, track fetal growth against expected milestones, and know roughly when to expect labor, even though the biology of individual pregnancies varies.
This calculator supports five different ways of estimating that date, because different people have different information available. Some know the first day of their last period precisely; others, particularly those who conceived through fertility treatment, know their exact conception or embryo transfer date, which can actually produce a more precise estimate than the standard LMP method.
How a Pregnancy Due Date Is Calculated
The most widely used method is Naegele's rule, developed in the nineteenth century and still the basis for the standard clinical estimate today. It assumes an average pregnancy length of 280 days, or 40 weeks, counted from the first day of the last menstrual period, and it assumes a textbook 28-day cycle with ovulation occurring around day 14. Because real cycles vary in length, this calculator lets you adjust the cycle length input, which shifts the estimated ovulation and due date accordingly.
LMP (Last Menstrual Period) Method
Due date = first day of LMP + 280 days, adjusted for cycle length. This is the most common method used at a first prenatal visit because the date is usually easy for a patient to recall, even before any scan has been performed.
Conception Date Method
If you know your approximate conception date — for example, from ovulation tracking or a single instance of intercourse — the due date is estimated as conception date + 266 days (38 weeks), since conception typically occurs roughly two weeks after the LMP in a standard cycle.
IVF Transfer Date Method
For pregnancies conceived through in-vitro fertilization, the embryo's exact age at transfer is known, which makes this one of the most accurate estimation methods available. For a day-5 blastocyst transfer, the due date is typically calculated as transfer date + 261 days; for a day-3 transfer, it is transfer date + 263 days.
Ultrasound Dating Method
An early ultrasound, particularly one performed in the first trimester, measures the fetus and estimates gestational age directly from its size. Because early fetal growth is highly consistent across pregnancies, first-trimester ultrasound dating is considered one of the most reliable methods, and it is commonly used to confirm or adjust a due date originally estimated from the LMP.
The Pregnancy Timeline at a Glance
A full-term pregnancy spans roughly 40 weeks from the LMP, divided into three trimesters that each bring distinct developmental milestones and physical changes.
| Trimester | Weeks | Key Milestones |
|---|---|---|
| First | 1–13 | Major organs begin forming; morning sickness and fatigue are common. |
| Second | 14–27 | Often called the most comfortable stage; fetal movement usually becomes noticeable. |
| Third | 28–40 | Rapid weight gain for the baby; body prepares for labor. |
Baby Growth, Week by Week
- Weeks 4–8: The neural tube, heart, and early limb buds begin to form.
- Weeks 9–13: Major organs are present in early form; the fetus is officially referred to as such rather than an embryo from week 11 onward.
- Weeks 14–19: Bones harden, and fine hair called lanugo appears on the skin.
- Weeks 20–27: Many people feel the first fetal movements; hearing begins to develop.
- Weeks 28–33: Rapid brain development and eye opening.
- Weeks 34–37: Lungs continue maturing in preparation for birth.
- Weeks 38–40: The baby is considered full term, and organ systems complete final preparation for life outside the womb.
These are general reference points; every pregnancy progresses at its own pace, and a healthcare provider tracking fetal growth through scans is always the most reliable source for your specific pregnancy.
Common Signs and Symptoms During Pregnancy
Symptoms vary widely between individuals and pregnancies, but commonly reported experiences include fatigue and nausea in the first trimester, increased energy and appetite in the second, and back discomfort or shortness of breath in the third as the uterus grows. Any unusual or severe symptom, particularly heavy bleeding, severe abdominal pain, or reduced fetal movement, should always be discussed with a healthcare provider promptly rather than waiting for a scheduled visit.
Healthy Pregnancy Tips
Nutrition
A varied diet rich in folate, iron, calcium, and protein supports both maternal health and fetal development. Many healthcare providers recommend a prenatal vitamin containing folic acid, ideally started before conception, to help reduce the risk of certain neural tube defects.
Exercise
Moderate activity such as walking, swimming, or prenatal yoga is generally encouraged throughout an uncomplicated pregnancy, though intensity and specific activities should always be discussed with your own provider based on your health history.
Medical Checkups and Prenatal Care
Regular prenatal visits allow a provider to track growth, blood pressure, and screening results, and to catch potential complications early. The recommended visit schedule typically becomes more frequent as the due date approaches.
What Can Affect Your Due Date
- Irregular or unusually long or short menstrual cycles.
- Uncertainty about the exact date of the last period.
- A discrepancy between LMP dating and early ultrasound measurements, in which case providers commonly favor the ultrasound estimate.
- Assisted reproduction, where the exact conception or transfer date is known precisely.
Common Myths About Due Dates
Myth: Most babies are born exactly on their due date. In reality, only a small minority of births happen on the estimated due date itself; a range of one to two weeks before or after is entirely normal.
Myth: A due date calculated from LMP is always less accurate than an ultrasound. For someone with very regular cycles, LMP dating can be quite close to an early ultrasound estimate; the two methods are typically used together to refine accuracy.
Expert Recommendations
Organizations such as the American College of Obstetricians and Gynecologists (ACOG) recommend that anyone who is pregnant or planning a pregnancy establish care with a qualified provider as early as possible, since early prenatal visits allow dating to be confirmed and any risk factors identified sooner. The CDC and World Health Organization both publish detailed, regularly updated guidance on prenatal care, nutrition, and warning signs worth reviewing alongside anything a calculator like this one can tell you.
Frequently Asked Questions
Conclusion
A due date calculator is a starting point, not a guarantee — it gives you a planning anchor so you can schedule prenatal care, understand roughly which trimester you're in, and follow along with general developmental milestones. Whichever method you use, the estimate is only ever as reliable as the date it's built on, so keep your prenatal appointments and let your healthcare provider refine or confirm your due date as your pregnancy progresses.
Reference sources used in preparing this guide include the American College of Obstetricians and Gynecologists, the Centers for Disease Control and Prevention, the World Health Organization, the National Institutes of Health, MedlinePlus, the NHS, and the Mayo Clinic. Always consult your own healthcare provider for guidance specific to your pregnancy.
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