Due Date Calculator

Your due date — officially called the Estimated Due Date (EDD) — marks the day your baby is expected to arrive, calculated as 280 days (40 weeks) from the first day of your Last Menstrual Period (LMP). This method, known as Naegele's Rule, is the standard used by gynaecologists in India and worldwide. Only about 5% of babies are born on their exact due date, but your EDD is the anchor that every prenatal appointment, scan, and screening test is scheduled around.

This due date calculator is for expectant mothers, partners, and families who want a quick, private estimate of when the baby is likely to arrive — and a clear map of the pregnancy week by week. It is most useful in early pregnancy, before your first dating scan, and as a handy reference between antenatal visits.

How it works: Naegele's Rule

The calculation adds 280 days (40 weeks) to the first day of your LMP. There is an equivalent shortcut that doctors have used for over a century: take your LMP date, add 1 year, subtract 3 months, and add 7 days. Both routes land on the same EDD. The method assumes a textbook 28-day menstrual cycle with ovulation on day 14, so pregnancy is counted from the LMP even though conception actually happens about two weeks later. This is why your "weeks pregnant" figure already shows around 2 weeks at the moment of conception.

A worked example

Suppose the first day of your last period was 15 January 2026. Adding 280 days gives an EDD of about 22 October 2026. Using the shortcut: 15 January 2026 + 1 year = 15 January 2027; minus 3 months = 15 October 2026; plus 7 days = 22 October 2026 — the same date. Your first trimester would run to around 9 April 2026 (end of week 12), the second trimester would begin near 16 April 2026 (week 14), and the third trimester near 30 July 2026 (week 28).

Trimester timeline

Pregnancy is divided into three trimesters. First trimester: weeks 1–12 — major organ development; this is when most morning sickness and fatigue occur. Second trimester: weeks 13–27 — often the most comfortable phase, when energy returns and the bump becomes visible; the anatomy (Level-2) scan happens at 18–20 weeks. Third trimester: weeks 28–40 — rapid fetal growth leading up to birth. Full term begins at week 37, and a pregnancy is considered post-term after 42 weeks.

Antenatal care milestones in India

Your EDD drives a recommended schedule of antenatal check-ups. A common pattern is: first visit at 8–12 weeks, then monthly visits up to 28 weeks, fortnightly visits from 28–36 weeks, and weekly visits from 36 weeks until delivery. Key milestones include the first dating/viability scan (around 6–12 weeks), the NT scan (11–13 weeks), the anatomy scan (18–20 weeks), and the glucose screening for gestational diabetes (24–28 weeks). Many Indian hospitals also align Tdap and iron-folic-acid supplementation with these visits.

Key tips and common notes

• Use your accurate LMP. If your periods are irregular or you are unsure of the exact date, the estimate becomes less reliable — note that for your doctor.
• The first-trimester ultrasound wins. An early dating scan (8–12 weeks) measures the baby and is more accurate than LMP math. If it differs from your LMP date by more than about a week, your gynaecologist will usually re-date the pregnancy to the scan.
• A range, not a deadline. Roughly 80% of babies arrive within two weeks on either side of the EDD. Think of it as the centre of a window, not a fixed appointment.
• Long or short cycles shift things. If your usual cycle is much longer or shorter than 28 days, your ovulation — and therefore your true conception date — may not be on day 14, so confirm with a scan.

This calculator gives an estimate for general information only — it is a planning aid, not medical advice. Your due date and pregnancy care should always be confirmed and managed by your doctor or gynaecologist.