🤰 Pregnancy Calculator
Enter the first day of your last menstrual period (LMP) and average cycle length to estimate your baby's due date and track your pregnancy week by week.
⚠️ Medical Disclaimer: This calculator is for informational purposes only. It does not substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of a physician for any health-related questions.
How is Gestational Week Calculated?
The calculation uses Naegele's Rule, which is the clinical standard worldwide:
1. Gestational Duration:
A full-term pregnancy is estimated at 280 days (40 weeks) from the first day of the last menstrual period (LMP).
2. Conception Date:
In a regular 28-day cycle, conception typically happens 14 days after LMP.
3. Trimesters:
- 1st Trimester: Weeks 1 - 12
- 2nd Trimester: Weeks 13 - 26
- 3rd Trimester: Weeks 27 - 40+.
Frequently Asked Questions
The due date is an estimate. Only about 4% of babies are born precisely on their calculated due date. Most babies arrive within a window of 2 weeks before or 2 weeks after the calculated date.
Yes. Standard due date calculations assume a regular 28-day cycle. If your cycle is longer (e.g., 32 days), your ovulation happened later, and your actual due date will be adjusted forward by a few days.
Early first-trimester ultrasounds measure crown-rump length, which is the most reliable way to date a pregnancy. If there is a discrepancy of more than 7 days, your obstetrician will likely adjust your official due date based on the scan.
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