Pregnancy Due Date Calculator
Pregnancy Due Date Calculator
How Is a Due Date Calculated?
An estimated due date (EDD) is a prediction of when a pregnant person will give birth. While it is called a "due date," it is important to remember that it is only an estimate. This calculator uses Naegele's rule, the standard method for calculating a due date based on the first day of your last menstrual period (LMP).
How to Use the Calculator
Simply use the date picker to select the first day of your last period. The calculator will automatically update with your estimated due date and other useful information about your pregnancy timeline.
Understanding Naegele's Rule
Naegele's rule is a simple formula used by healthcare providers to estimate the due date. The calculation is based on a standard 28-day menstrual cycle where ovulation is presumed to occur on day 14. The formula works by adding 280 days (or 40 weeks) to the first day of your last menstrual period. This 40-week period includes the approximately two weeks before actual conception.
The Trimesters of Pregnancy
A pregnancy is divided into three trimesters, each marking a distinct phase of fetal development.
| Trimester | Weeks | Key Developments |
|---|---|---|
| First | 1 - 13 | The baby's body structure and organ systems develop. Most major organs are formed by the end of this trimester. |
| Second | 14 - 27 | Often called the "golden period" as early pregnancy symptoms subside. The baby's features become more defined, and you may feel movement. |
| Third | 28 - 40+ | The baby grows rapidly in size and weight, and the organs mature. The baby settles into a head-down position in preparation for birth. |
A Due Date Is Only an Estimate
It is important to understand that the estimated due date is not a guarantee. In fact, only about 5% of babies are born on their exact due date. Most babies are born within a week or two of their EDD. Your healthcare provider may adjust your due date based on an ultrasound, which can provide a more accurate age for the fetus, especially if your menstrual cycles are irregular.
Disclaimer: This calculator provides an estimate for informational purposes and is not a substitute for professional medical advice. Always consult with your doctor or midwife for guidance regarding your pregnancy.