Due Date Calculator
Estimate your pregnancy due date and current gestational week based on the first day of your last menstrual period, using the standard Naegele’s rule method.
How due dates are estimated
The most common method for estimating a pregnancy due date is Naegele’s rule, which adds 280 days (40 weeks) to the first day of your last menstrual period (LMP). This assumes a typical 28-day cycle with ovulation around day 14.
How this calculator works
Enter the first day of your last period and your average cycle length. The calculator adds 280 days to your LMP date, adjusting slightly for cycles longer or shorter than 28 days, to estimate your due date. It also shows your current gestational age in weeks and days, which trimester you’re likely in, and how many days remain until your estimated due date.
Only a small percentage of babies are actually born on their exact due date; a full-term range generally spans a couple of weeks before or after. This tool provides a general estimate for planning and educational purposes only and is not a substitute for dating confirmed by a healthcare provider, such as through an ultrasound.