Pregnancy Due Date Calculator
Calculate your estimated due date, current week, and trimester based on your last menstrual period. See key milestones along the way.
How Due Dates Are Calculated
This calculator uses Naegele's rule: add 280 days (40 weeks) to the first day of your last menstrual period. It was formulated in the early 1800s and remains the standard first-pass estimate used by OB-GYNs worldwide.
Only about 4% of babies arrive on their exact due date. Most births occur between weeks 38 and 42. Your doctor may adjust the date after an early ultrasound, which can be more accurate than LMP-based calculation — especially for people with irregular cycles.
First Trimester vs. Second vs. Third
The first trimester (weeks 1-12) is when major organ development happens. The second trimester (13-26) is often called the "honeymoon period" — morning sickness typically fades and energy returns. The third trimester (27-40) is focused on growth and preparation for birth. Each stage has different nutritional needs — our Calorie Calculator can help you adjust your intake accordingly.
⚠️ Medical Disclaimer
This tool provides estimates for informational purposes only. It is not a substitute for professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider before making health decisions. Results may vary based on individual factors not captured by this calculator.