How is the due date calculated?

The standard method (Naegele's rule) adds 280 days (40 weeks) to the first day of your last menstrual period. If you know the conception date, we add 266 days instead.

How accurate is the due date?

Only about 4% of babies are born exactly on the due date. Most arrive within two weeks before or after. An early ultrasound is the most accurate way to estimate.

What are the three trimesters?

First trimester: weeks 1–12. Second: weeks 13–27. Third: weeks 28 to birth. Each trimester has different developmental milestones and screening tests.

Can the due date change?

Yes. If an early ultrasound shows a different gestational age than LMP-based dating, your doctor may adjust the due date — usually only if the difference is more than 5–7 days.

What is the difference between gestational age and fetal age?

Gestational age is counted from the last menstrual period — the standard medical convention. Fetal age is counted from conception, which is about two weeks later. So at 12 weeks gestational age, the fetus is about 10 weeks old.

What is full term, early term and late term?

Full term is 39–40 weeks. Early term is 37–38 weeks. Late term is 41 weeks. Post-term is 42+ weeks. Babies born before 37 weeks are considered premature, and doctors may induce at 41–42 weeks to reduce risk.

Pregnancy Due Date Calculator

Estimate your baby's due date from your last menstrual period or the conception date. See your current week, trimester and the number of days remaining. Based on Naegele's rule — the standard 280-day count used by obstetricians.

How to use

Choose your method

Select Last menstrual period (LMP) or Conception date.

Enter the date

Type the first day of your last period or the conception date.

Read your due date

See your estimated due date, current week and trimester.

Features

Two calculation methods

Based on last menstrual period (LMP) or conception date.

Current pregnancy week

See which week of pregnancy you are in right now.

Trimester indicator

Know whether you are in the first, second or third trimester.

Days until due date

See exactly how many days remain until your estimated due date.

Common use cases

Estimate your baby's due date
Track which week of pregnancy you are in
See how many days remain until the due date
Plan prenatal appointments by trimester

Frequently Asked Questions

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