How is pregnancy due date calculated?

The most common method is Naegele's Rule: add 280 days (40 weeks) to the first day of your Last Menstrual Period (LMP). Alternatively: add 9 months and 7 days to the LMP date. This gives the Estimated Due Date (EDD). Only about 5% of babies are born exactly on the EDD; most births occur between weeks 38–42.

How many weeks is a full-term pregnancy?

A full-term pregnancy lasts 40 weeks (280 days) from the first day of the last menstrual period. Delivery between 37 and 42 weeks is considered normal. Before 37 weeks is premature; after 42 weeks is post-term.

What are the three trimesters of pregnancy?

First trimester: weeks 1–12 (conception to end of month 3). Second trimester: weeks 13–26 (months 4–6). Third trimester: weeks 27–40 (months 7–9). Each trimester has distinct development milestones and medical checkups recommended.

Pregnancy Due Date Calculator India – Baby Birth Date Estimator

Pregnancy Details

First Day of Last Menstrual Period (LMP)

Select the first day of your last period

Average Cycle Length (days)

Average cycle is 28 days. Longer cycles shift the due date later.

Naegele's Rule

Due Date = LMP + 280 days (40 weeks). Conception is assumed around day 14 of your cycle. Actual birth typically occurs between week 38 and 42.

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Select your LMP date above to see your expected due date

The Three Trimesters

First Trimester (Weeks 1–12)

Baby's organs and systems begin forming. Morning sickness is common. Critical period for fetal development. First ultrasound recommended at 8–12 weeks.

Second Trimester (Weeks 13–26)

Baby's movements become noticeable (quickening). Energy levels improve. Anatomy scan at 18–20 weeks. Baby develops hearing and can respond to sounds.

Third Trimester (Weeks 27–40)

Rapid weight gain. Baby's lungs mature. Frequent check-ups. Baby settles into birth position. Most deliveries happen between weeks 38–42.

Important Pregnancy Tips

→Folic acid — take 400mcg/day from the time you plan to conceive through the first 12 weeks to prevent neural tube defects.
→First ANC visit — schedule your first antenatal check-up within 8–10 weeks of pregnancy confirmation.
→Due dates vary — only about 5% of babies arrive exactly on the due date. A range of ±2 weeks (38–42 weeks) is completely normal.
→Always consult your doctor — use this calculator as a guide. Your OB/GYN will confirm your dates via ultrasound.

Frequently Asked Questions

Common questions about pregnancy due dates

How accurate is the due date calculator?

This calculator uses Naegele's Rule (LMP + 280 days), the standard used by doctors worldwide. It assumes a regular 28-day cycle. For irregular cycles, adjust the cycle length. Your doctor may revise the EDD based on your first trimester ultrasound, which is the most accurate dating method.

What is the difference between LMP and conception date?

LMP (Last Menstrual Period) is the standard start point for pregnancy dating. Conception happens approximately 14 days after LMP (at ovulation). Pregnancy is conventionally counted from LMP (40 weeks total), even though conception occurs about 2 weeks later (so the fetus is actually 38 weeks old at birth).

What week is full term pregnancy?

Full term is defined as 39 to 40 weeks 6 days. Early term is 37–38 weeks 6 days. Late term is 41–41 weeks 6 days. Post term is 42+ weeks. Preterm (premature) is before 37 weeks.

When should I schedule my first doctor visit?

Schedule your first prenatal (antenatal care / ANC) appointment as soon as you confirm your pregnancy, ideally by 8 weeks. Your doctor will confirm the pregnancy, estimate your due date via ultrasound, and recommend blood tests and supplements like folic acid and iron.