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Pregnancy Due Date Calculator

Calculate your pregnancy due date from last period (LMP) or conception date. Track gestational age and key milestones.

Calculating Your Due Date

Pregnancy is dated from the first day of your last menstrual period (LMP), making a full-term pregnancy 40 weeks.

Naegele's Rule

The standard method: LMP + 280 days = Due Date

  • Assumes 28-day cycle
  • Assumes ovulation on day 14
  • Actual conception is about 2 weeks after LMP

Pregnancy Milestones

  • Week 8: First ultrasound, heartbeat visible
  • Week 12: End of first trimester
  • Week 20: Anatomy scan, may learn gender
  • Week 24: Viability milestone
  • Week 37: Full term begins

Understanding Trimesters

  • First (1-12 weeks): Major organ formation, highest miscarriage risk
  • Second (13-26 weeks): Often called the "honeymoon period," baby movement felt
  • Third (27-40 weeks): Rapid growth, preparation for birth

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Frequently Asked Questions

How is due date calculated?

Using Naegele's rule: LMP + 280 days (40 weeks). Conception-based: conception date + 266 days (38 weeks).

What is gestational age?

The age of the pregnancy counted from the first day of the last menstrual period (LMP), not conception.

How accurate is the due date?

Only about 5% of babies are born on their due date. Full term is 37-42 weeks. Ultrasound dating is most accurate.

What are the trimesters?

First: weeks 1-12, Second: weeks 13-26, Third: weeks 27-40. Each has different milestones and development.