How the Pregnancy Due Date Calculator Works
The estimated due date (EDD) is typically calculated using Naegele's rule: add 280 days (40 weeks) to the first day of your last menstrual period (LMP). If your cycle length differs from the standard 28 days, the calculator adjusts by adding or subtracting the difference. When using a known conception date, 266 days (38 weeks) are added, since conception typically occurs about 14 days after the LMP.
Trimester Breakdown
Pregnancy is divided into three trimesters. The first trimester (weeks 1–12) is a period of rapid development when major organs begin to form. The second trimester (weeks 13–26) is often called the "golden period" as many early symptoms ease. The third trimester (weeks 27–40) is when the baby gains most of its weight and prepares for birth.
Accuracy
Only about 5 % of babies are born on their exact due date. Most births occur within two weeks before or after the EDD. An ultrasound scan in the first trimester provides the most accurate dating. This calculator gives an estimate — your healthcare provider will confirm your due date with clinical assessments.
Medical Disclaimer: This tool is for informational and educational purposes only. It does not replace professional medical advice, diagnosis, or treatment. Always consult your obstetrician, midwife, or healthcare provider for pregnancy-related decisions.