Pregnancy Due Date Calculator
Enter the first day of your last menstrual period to estimate your due date.
FAQ
How is the due date calculated?
This calculator uses Naegele's Rule, the standard method: it adds 280 days (40 weeks) to the first day of your last menstrual period, assuming a typical 28-day cycle.
How accurate is this estimate?
It's an estimate, not a guarantee — only a small percentage of babies arrive exactly on their calculated due date. Actual delivery can happen anywhere from a couple of weeks before to two weeks after, and cycle length variations affect accuracy.
What if my cycle isn't 28 days?
This calculator assumes a standard 28-day cycle. If yours is significantly longer or shorter, your actual conception date — and due date — may differ; an ultrasound dating scan from a healthcare provider gives a more personalized estimate.
What are the trimesters?
Pregnancy is typically divided into three trimesters: first trimester (weeks 1-13), second trimester (weeks 14-27), and third trimester (weeks 28 to birth).
About this tool
This calculator estimates a pregnancy due date using Naegele's Rule, based on the first day of your last menstrual period, and shows your current estimated week and trimester. This is an estimate for general reference only, not medical advice — always confirm dates with a healthcare provider.