Pregnancy & Due Date Calculator
Enter your last menstrual period to find your estimated due date, pregnancy week and important milestone dates.
Find Your Estimated Due Date
Pregnancy lasts an average of 40 weeks (280 days) from the last menstrual period (LMP). This tool calculates your estimated due date using the Naegele formula, the most widely used method worldwide, and also shows which week and trimester you are in along with important check-up and screening dates.
This tool is for informational purposes only. The estimated due date may differ from ultrasound findings and your doctor's assessment. Do not miss regular check-ups during pregnancy.
What Is the Naegele Formula?
Described by Franz Karl Naegele in the 19th century, this formula is calculated as Last Menstrual Period + 280 days (or + 9 months + 7 days). It carries an error margin of approximately 5%, assuming a regular 28-day cycle. An ultrasound-based due date may differ by 1–2 weeks — this is normal.
Pregnancy Trimesters
| 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 |
Key Points to Watch During Pregnancy
- 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 assessing all of the baby's organ structures — plan the appointment early.
- Folic acid supplementation should begin before conception and continue for at least the first 12 weeks.