Pregnancy Due Date Calculator

How this estimate is calculated

This uses Naegele's rule, the standard clinical starting point: adding 280 days (40 weeks) to the first day of the last menstrual period, assuming a typical 28-day cycle. If your average cycle is longer or shorter than 28 days, this tool adjusts the estimate by the difference, which is a common refinement — a longer cycle generally means ovulation happens later, pushing the estimated due date later too.

Why this is an estimate, not a prediction

Only a small percentage of babies are actually born on their exact calculated due date — most arrive within a week or two either side of it. An early ultrasound is significantly more accurate than a last-period-based calculation, especially for anyone with irregular cycles. This tool is meant for general planning and awareness, not as medical guidance — talk with a healthcare provider for a clinically confirmed estimate and any decisions about your pregnancy.