Pregnancy Due Date Calculator — Private & Confidential
Estimate your pregnancy due date using Naegele's rule. Enter your last menstrual period or conception date. See your current week, trimester, and key milestones. Everything is calculated in your browser — your health information is never uploaded, stored, or shared.
Key Milestones
How the Due Date Calculator Works
This calculator uses Naegele's rule, the standard medical method for estimating pregnancy due dates. From the Last Menstrual Period (LMP), the estimated due date is calculated by adding 280 days (40 weeks). If you provide a conception date instead, the calculator adds 266 days (38 weeks), since conception typically occurs about 14 days after the LMP.
Naegele's Rule
Due Date = LMP + 280 days (40 weeks)
Due Date = Conception Date + 266 days (38 weeks)
Most pregnancies last between 37 and 42 weeks. The estimated due date represents the midpoint of this range. Only about 5% of babies are born on their exact due date.
Understanding Trimesters
Pregnancy is divided into three trimesters. The first trimester spans weeks 1-12 and involves rapid cell division and organ formation. The second trimester (weeks 13-26) is often considered the most comfortable period, with the baby growing significantly. The third trimester (weeks 27-40) prepares both mother and baby for delivery, with the baby gaining weight and the lungs maturing.
Important Disclaimer
This calculator provides an estimate only and is not a substitute for professional medical advice. Ultrasound dating performed by your healthcare provider is the most accurate method for determining gestational age and due date. Always consult your doctor or midwife for personalized prenatal care.