Due Date Calculator & Early Health Charts

An Estimated Delivery Date (EDD) represents the projected date on which a pregnant woman will reach 40 completed weeks of gestation (280 days), calculated from the first day of her last menstrual period (LMP). This standard clinical methodology assumes a baseline 28-day menstrual cycle with ovulation occurring on Day 14.

The standard clinical method for calculating due dates is Naegele's Rule, devised by 19th-century German obstetrician Franz Karl Naegele. The rule calculates EDD by taking the first day of the last menstrual period, adding 7 days, subtracting 3 months, and adding 1 year.

For women with non-standard cycle lengths (shorter or longer than 28 days) or known ovulation dates (such as in IVF or tracked cycles), adjusted calculations offer superior precision. Adding or subtracting the difference between your average cycle length and 28 days refines the estimated delivery date accordingly.

Our Pregnancy Due Date Calculator allows you to calculate your EDD using multiple input methods: Last Menstrual Period (LMP), Conception Date, IVF Transfer Date, or Ultrasound Date. This gives you an accurate gestational timeline and weekly fetal development milestones.

It is important to recognize that an estimated due date is an educated biological target rather than a strict deadline. Only about 4% to 5% of babies are born on their exact predicted due date. However, roughly 90% of healthy pregnancies deliver within a two-week window before or after the EDD (between 38 and 42 weeks gestation).

First-trimester ultrasound (performed between 8 and 13 weeks) measuring Crown-Rump Length (CRL) is considered the most accurate method for determining gestational age. If an early ultrasound differs from LMP calculations by more than 5 days, Obstetric guidelines recommend adjusting the official due date to match the ultrasound measurements.

Maternal age, parity (whether this is a first or subsequent pregnancy), genetic factors, and placental health can also influence spontaneous labor timing. First-time mothers statistically tend to deliver slightly after their calculated due date (average 40 weeks and 3 days), whereas subsequent pregnancies often deliver slightly earlier.

Understanding your EDD allows your medical team to schedule vital prenatal care milestones—such as first-trimester screening, anomaly scans, glucose tolerance testing, and group B strep screening—at precise gestational windows for optimal maternal-fetal outcomes.

Our calculator provides a complete gestational summary: your official Estimated Delivery Date, current gestational age in weeks and days, current trimester, and estimated fetal size benchmarks (comparing your baby to familiar fruits or vegetables).

As you progress through your pregnancy timeline, key physical milestones mark your baby's growth. By week 8, main organs and limb buds begin forming; by week 12, reflexes develop; by week 20, movement (quickening) is felt; by week 24, fetal viability is reached; by week 37, early full term is attained.

Use your due date roadmap to plan practical milestones: scheduling birth classes during month 6 or 7, completing nursery setup by week 34, packing your hospital bag by week 36, and preparing for labor signals as you enter week 37.

If your pregnancy reaches 41 completed weeks without spontaneous labor, your midwife or obstetrician will discuss post-term surveillance (non-stress tests and amniotic fluid checks) and potential labor induction options to ensure ongoing fetal safety.

How is a due date calculated for IVF pregnancies? For IVF pregnancies, the due date is calculated based on the embryo transfer date and embryo age (e.g., 3-day or 5-day blastocyst). Adding 266 days to the equivalent ovulation date gives exact due date precision.

Can my due date change during pregnancy? Yes. If a first-trimester ultrasound shows a discrepancy of more than 5 days compared to your LMP calculation, your healthcare provider will update your official due date to match the ultrasound.

What is the difference between gestational age and fetal age? Gestational age is measured from the first day of your last period (LMP) and is the standard medical timeline (40 weeks total). Fetal age (conception age) is measured from actual fertilization (usually 2 weeks after LMP, totaling 38 weeks).

What happens if I pass my due date without labor starting? Passing your due date (reaching 40 weeks) is very common. Most providers monitor post-date pregnancies closely with biophysical profiles and consider gentle induction between 41 and 42 weeks if labor does not begin naturally.