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Due Date Calculator

Calculate your estimated due date (EDD), current pregnancy week, trimester, and key milestones. Enter your last menstrual period date or conception date. Date results formatted for your region.

Pregnancy Due Date Calculator

LMP or conception date → EDD · week · trimester · milestones

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Estimated Due Date

This is an estimate based on Naegele's rule. Your healthcare provider may adjust the due date based on ultrasound measurements.

Naegele's rule: EDD = LMP + 280 days (adjusted for cycle length). For cycles longer than 28 days, conception — and therefore the EDD — is shifted by the additional days. For conception date entry, EDD = conception + 266 days.

Pregnancy Timeline — Key Dates & Milestones

WeekMilestoneTrimester
Week 4Positive pregnancy test possible1st
Week 6–8Heart begins beating (ultrasound detectable)1st
Week 11–13Nuchal translucency scan & first trimester screening1st
Week 16–20Anatomy scan; gender may be visible; quickening (movement felt)2nd
Week 24Viability — survival outside womb possible with intensive care2nd
Week 28Third trimester begins; glucose tolerance test3rd
Week 36Early term — baby mostly developed, lungs maturing3rd
Week 39–40Full term — optimal birth window3rd

Understanding Your Due Date

Your estimated due date (EDD) is exactly that — an estimate. Only about 5% of babies are born on their due date, and approximately 80% arrive within 10 days of it. Babies born between 39 and 40 weeks have the best outcomes statistically — this is "full term." Births from 37–38 weeks are "early term" and slightly higher risk than 39–40 weeks. Births from 41–42 weeks are "late term." Post-term (beyond 42 weeks) carries increasing placental risk, which is why induction is typically offered at 41–42 weeks depending on local guidelines. Understanding the range of normal birth timing can reduce anxiety about your baby's exact arrival date.

Frequently Asked Questions

Naegele's rule: add 280 days to the first day of your last period. This assumes a 28-day cycle with ovulation on day 14. For longer cycles, the EDD shifts later by the excess days. A first trimester ultrasound (crown-rump length) provides a more accurate EDD than LMP calculation, particularly for women with irregular cycles.
First trimester (weeks 1–13): Embryonic development of all major organs. Highest miscarriage risk. Second trimester (weeks 14–27): Nausea typically resolves, energy returns, fetal movements begin. Third trimester (weeks 28–40): Rapid fetal weight gain, lung maturation, preparation for birth. Each trimester has distinct physiological changes for both mother and baby.
Only ~5% of babies arrive on their EDD. Approximately 80% are born within 10 days either side. LMP calculation accuracy depends on cycle regularity (±2 weeks); first-trimester ultrasound is accurate to ±5 days. If LMP and ultrasound dates differ by more than 7–10 days, the ultrasound date is typically used.
The current medical viability threshold is approximately 22–24 weeks, though survival rates at 22 weeks are very low (5–10%) and increase progressively with each additional week. At 28 weeks, survival with intensive care is above 90%. At 32 weeks, survival exceeds 99% and most outcomes are comparable to term. Advances in neonatal intensive care have pushed the viability threshold earlier over the past two decades.

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