Pregnancy & Due Date Calculator
Enter the first day of your last period to see how many weeks pregnant you are and your estimated due date.
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This tool is for information only and does not replace your doctor. The estimated due date may differ from ultrasound findings and your doctor's assessment. Keep up regular check-ups during pregnancy.
How Is Pregnancy Week Calculated?
Doctors count pregnancy from the first day of the last menstrual period (LMP). An average pregnancy lasts 40 weeks (280 days). This tool uses Naegele's rule: add 7 days to the first day of your last period, then go back 3 months to get the estimated due date.
What Are the Trimester Periods?
Pregnancy is divided into three periods called trimesters. Each one brings different physical and hormonal changes.
| Period | Weeks | Key Developments |
|---|---|---|
| 1st Trimester | Weeks 1–12 | Organ development, heartbeat begins, nausea and vomiting |
| 2nd Trimester | Weeks 13–26 | Movements felt, sex can be determined, nausea subsides |
| 3rd Trimester | Weeks 27–40 | Rapid growth, preparation for birth, position monitoring |
Why Your Pregnancy Week Matters
Every week brings different developments in your baby and your body. Knowing your pregnancy week helps you time screening tests, follow the baby's development and plan for the birth. Keep in mind that only 5% of babies are born on the exact calculated date. The date is an estimate.
- In the first trimester, do not miss the NT ultrasound and maternal blood screening (combined test, weeks 11–13+6).
- The OGTT test at weeks 24–28 screens for gestational diabetes (GDM). Early detection is important.
- The week 20 anomaly ultrasound is the most comprehensive scan for checking all of the baby's organs. Book the appointment early.
- Folic acid supplementation should begin before conception and continue for at least the first 12 weeks.