How is my due date calculated?

Naegele's rule: Add 280 days (40 weeks) to the first day of your last menstrual period. This assumes a 28-day cycle with ovulation on day 14.

How accurate is the due date?

Only about 4% of babies are born on their due date. Most arrive within 2 weeks before or after.

Pregnancy Calculator

Calculate your due date, current trimester, weeks pregnant, and key fetal development milestones.

First Day of Last Period

Average Cycle Length (days)

How Pregnancy Is Calculated

Pregnancy is measured from the first day of your last menstrual period (LMP). This is called the gestational age. Conception typically occurs about 14 days after LMP in a 28-day cycle.

Key Pregnancy Milestones

Week 4: Implantation occurs, pregnancy test turns positive
Week 8: Heartbeat detectable on ultrasound
Week 12: End of first trimester, miscarriage risk drops significantly
Week 20: Anatomy scan, may reveal baby's sex
Week 24: Viability milestone — baby has a chance of survival if born
Week 37: Baby is considered full-term

The Three Trimesters

First Trimester (Weeks 1-12): Rapid cell division, organ formation. Most common for nausea and fatigue.
Second Trimester (Weeks 13-26): Growth phase. Most women feel best during this period. Baby movements felt ("quickening").
Third Trimester (Weeks 27-40): Rapid brain development, fat accumulation. Common discomforts: back pain, swelling, shortness of breath.

Important Notes

Only ~4% of babies arrive on their due date. First-time moms often go past their due date; subsequent pregnancies tend to arrive sooner.

Your Pregnancy Timeline

Due Date

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Weeks Pregnant

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Current Trimester

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Conception Date

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Days Until Due Date

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