👶 Due Date Calculator

Our Due Date Calculator estimates your pregnancy due date using your last menstrual period (LMP) and average cycle length. Pregnancy typically lasts about 40 weeks (280 days) from the first day of your LMP. This tool also estimates your conception date and shows how far along you are based on the current date.

The standard Naegele's Rule adds 280 days (40 weeks) to the first day of the last menstrual period. The calculator adjusts for cycle length: if your cycle is longer than 28 days, the due date shifts forward proportionally. The conception date is estimated as approximately 14 days after LMP (around ovulation), adjusted for cycle length.

1. Select the first day of your last menstrual period using the date picker.
2. Enter your average cycle length in days (default is 28).
3. Click Calculate to see your estimated due date, conception date, and current pregnancy week.

How accurate is the due date?

Only about 5% of babies are born exactly on their due date. The estimate is most accurate for women with regular 28-day cycles and known LMP.

What if my cycles are irregular?

If your cycle length varies significantly, an early ultrasound measurement is more accurate for dating the pregnancy.

When is my baby due if I know the conception date?

Add 266 days (38 weeks) from the conception date to estimate the due date.

How is the due date calculated?

The standard method is Naegele's Rule: add 280 days (40 weeks) to the first day of your Last Menstrual Period (LMP). This assumes a 28-day cycle with ovulation on day 14. If your cycle is longer or shorter, the calculator adjusts accordingly — for example, a 35-day cycle pushes the due date back by 7 days. An alternative method uses the conception date + 266 days. First-trimester ultrasound measurements (crown-rump length) are the most accurate dating method, with a margin of error of just 5–7 days.

How accurate is the due date?

Only about 5% of babies are born on their exact due date. About 60% are born within one week of the due date, and 90% within two weeks. First babies tend to arrive about 8 days late on average. The due date is a midpoint estimate, not a deadline — arriving anywhere between 37 weeks (full term) and 42 weeks is considered normal. Your healthcare provider may recommend induction if pregnancy extends past 41 weeks, as the placenta's efficiency declines and stillbirth risk increases slightly.

What are the early signs of pregnancy?

The most common early signs include a missed period (the most reliable sign), tender breasts, fatigue, nausea (morning sickness, which can occur at any time of day), increased urination, and mild cramping or spotting (implantation bleeding, lighter than a period). A home pregnancy test can detect hCG hormone in urine about 10–14 days after conception — testing first morning urine gives the most accurate result. For confirmation, see a healthcare provider for a blood test or ultrasound.

What is a trimester and how do they differ?

Pregnancy is divided into three trimesters of roughly 13 weeks each. First trimester (weeks 1–13): major organs form; risk of miscarriage is highest; morning sickness is common. Second trimester (weeks 14–27): often the most comfortable period; baby's sex can be determined; you may feel movement (quickening) around week 20. Third trimester (weeks 28–40+): baby gains most of its weight; physical discomfort increases (back pain, swelling, shortness of breath); weekly checkups begin around week 36. Each trimester has specific screening tests and milestones.

Schedule your first prenatal appointment soon after a positive pregnancy test. Keep track of your cycle lengths before pregnancy for the most accurate due date estimate. Remember that the due date is an estimate — full-term delivery can occur anywhere from 37 to 42 weeks.