Due Date Calculator
Find out when your little one will arrive. Choose your preferred calculation method below.
Calculate your due date
28
Default is 28 days. Normal cycle length is 21–35 days.
How is my due date calculated?
The most common method uses Naegele's rule: add 280 days (40 weeks) to the first day of your last menstrual period (LMP). This assumes a standard 28-day cycle. If your cycle is longer or shorter, the calculator adjusts automatically.
Three calculation methods
- Last Period (LMP): The standard method. Uses the first day of your last menstrual period plus 280 days, adjusted for your cycle length.
- Ovulation / Conception: If you know your ovulation or conception date, this method adds 266 days from that date.
- IVF Transfer: For IVF pregnancies, the calculation uses your embryo transfer date minus the embryo age (day 3 or day 5).
How accurate is this calculator?
A due date calculator provides an estimate. Only about 4% of babies are born on their exact due date, and most births occur within a two-week window around the estimated date. An ultrasound performed at 18–20 weeks provides the most accurate dating.