Due Date Calculator
Free Pregnancy Due Date Calculator
Our due date calculator estimates your baby's arrival date based on either your last menstrual period (LMP) or estimated conception date. Using the standard medical calculation of 280 days (40 weeks) from LMP or 266 days (38 weeks) from conception, you can get a reliable estimate of your due date along with your current pregnancy progress, trimester information, and key milestone dates.
How to Use
Select your calculation method: "Last Menstrual Period" if you know the first day of your last period, or "Conception Date" if you know the approximate date of conception. Enter the date using the date picker, then click "Calculate Due Date." You will see your estimated due date, current week of pregnancy, trimester, a visual progress bar, and key milestone dates for each trimester.
FAQ
How is the due date calculated?
When using the Last Menstrual Period (LMP) method, the due date is calculated by adding 280 days (40 weeks) to the first day of your last menstrual period. This is known as Naegele's rule. When using the conception date, 266 days (38 weeks) are added, since conception typically occurs about 2 weeks after the start of the last period.
How accurate is the estimated due date?
Only about 5% of babies are born on their exact due date. The estimated due date provides a general timeframe, and most babies are born within 2 weeks before or after the due date. An ultrasound performed in the first trimester can provide a more accurate estimate.
What are the three trimesters?
Pregnancy is divided into three trimesters. The first trimester covers weeks 1 through 12, during which major organ systems begin to form. The second trimester spans weeks 13 through 26, when the baby grows rapidly and movement becomes noticeable. The third trimester runs from week 27 to 40, during which the baby gains weight and prepares for birth.
What if I do not know my LMP date?
If you do not remember the date of your last menstrual period, your healthcare provider can estimate your due date using an ultrasound, typically performed during the first trimester. Early ultrasounds measure the size of the embryo and can estimate gestational age within a few days.
Can my due date change during pregnancy?
Yes, your due date may be adjusted based on ultrasound findings, especially if there is a significant discrepancy between the ultrasound-estimated age and the LMP-based calculation. Your doctor may update the due date if the difference is more than one week in early pregnancy or more than two weeks later on.