Pregnancy Due Date Calculator
Calculate your expected due date, current week of pregnancy and key milestones.
EDD is calculated using Naegele's rule: LMP + 280 days. Only ~5% of babies are born on their exact due date. ±2 weeks is normal.
How the due date (EDD) is calculated
EDD stands for Estimated Due Date — the date your baby is expected to arrive. Naegele's rule is the standard method for calculating it: take the first day of your last menstrual period (LMP) and add 280 days (40 weeks). It assumes a regular 28-day cycle with ovulation on day 14, which is why an early dating ultrasound is used to confirm or adjust the estimate.
Trimester timeline
A 40-week pregnancy is divided into three trimesters. This mini-reference shows the week ranges and what each stage broadly covers, measured from the first day of your last menstrual period.
Organ formation and early development. The first-trimester (NT) scan is usually done around week 12.
Steady growth and movement. The detailed anomaly scan is typically performed around weeks 18–20.
Rapid weight gain and lung maturation. Full term is reached from week 37 onward, leading up to the due date.
Frequently asked questions
What is EDD?
EDD stands for Estimated Due Date — the date your baby is expected to be born, roughly 40 weeks (280 days) from the first day of your last menstrual period. It is an estimate rather than a fixed date; most babies arrive within about two weeks either side of it.
How is the due date calculated?
The due date is calculated using Naegele's rule: add 280 days (40 weeks) to the first day of your last menstrual period (LMP). A common shortcut is to add one year, subtract three months and add seven days. If you know your conception date instead, add 266 days (38 weeks).
How accurate is the due date?
The due date is an estimate. Only about 1 in 20 babies are born on their exact due date, and arriving within two weeks before or after is considered normal. An early dating ultrasound (around 6–12 weeks) gives the most accurate estimate, especially if your cycle is irregular or you are unsure of your LMP.
How accurate is the LMP-based due date calculation?
The LMP method assumes a perfect 28-day cycle with ovulation on day 14. In reality, cycle lengths vary (21–35 days is normal) and ovulation timing varies. An early ultrasound (6–12 weeks) provides a more accurate due date and is recommended for all pregnancies.
What is a full-term pregnancy in India?
A pregnancy is considered full term at 39–40 weeks gestation. Early term is 37–38 weeks, late term is 41 weeks, and post-term is 42+ weeks. Most Indian hospitals aim to deliver between 39–41 weeks unless there are complications.
What are the three trimesters of pregnancy?
First trimester: weeks 1–13 (organ formation, highest miscarriage risk). Second trimester: weeks 14–27 (foetal growth, anatomy scan at 20 weeks). Third trimester: weeks 28–40+ (rapid weight gain, lung maturation, preparation for birth).
When is the anomaly scan done in India?
The detailed anomaly scan (Level 2 ultrasound) is typically done between 18–20 weeks gestation to check foetal anatomy and growth. Most government hospitals and private clinics in India offer this as part of routine antenatal care. The PNDT Act governs ultrasound use in India.
What if my cycle is longer or shorter than 28 days?
Adjust the LMP calculation by the difference from 28 days. If your cycle is 35 days (7 days longer), ovulation occurred 7 days later, so add 7 days to the calculated EDD. If your cycle is 21 days (7 days shorter), subtract 7 days. An early dating ultrasound eliminates this uncertainty.