A due date calculator helps expectant parents predict their baby's birth date. This tool uses your last menstrual period to estimate delivery. Typically, pregnancy lasts about 40 weeks.
Knowing your due date assists with pregnancy planning. Furthermore, it helps schedule important prenatal appointments. Additionally, it allows for better preparation for the baby's arrival.
Your due date is the estimated date when your baby will be born. Doctors calculate it as 40 weeks from your last period. However, only about 5% of babies arrive exactly on this date.
Most deliveries occur between 37-42 weeks. Consequently, your due date provides a helpful timeframe. Moreover, it serves as a guide for monitoring fetal development.
Simply enter the first day of your last period. Our calculator adds 280 days (40 weeks) to determine your estimated due date. This method is known as Naegele's Rule.
Remember, this calculation provides an estimate. Always consult your healthcare provider for confirmation. They may adjust your due date based on ultrasound measurements.
The standard medical formula for calculating due date is:
Due Date = First day of LMP + 280 days
Alternatively: LMP date + 9 months + 7 days
Our due date calculator uses a proven medical formula. It adds 280 days to your last menstrual period start date. This method assumes a regular 28-day cycle.
First, it identifies the first day of your last period. Then, it calculates 40 weeks forward from that date. Finally, it displays your estimated delivery date.
However, actual pregnancy duration varies. Factors like cycle length and ovulation timing affect accuracy. Therefore, consider this result an estimate.
| Last Menstrual Period | Estimated Due Date | Trimester Timeline |
|---|---|---|
| January 1, 2024 | October 7, 2024 | 1st: Jan-Mar, 2nd: Apr-Jun, 3rd: Jul-Oct |
| March 15, 2024 | December 19, 2024 | 1st: Mar-May, 2nd: Jun-Aug, 3rd: Sep-Dec |
| June 1, 2024 | March 8, 2025 | 1st: Jun-Aug, 2nd: Sep-Nov, 3rd: Dec-Mar |
| August 20, 2024 | May 27, 2025 | 1st: Aug-Oct, 2nd: Nov-Jan, 3rd: Feb-May |
| October 10, 2024 | July 17, 2025 | 1st: Oct-Dec, 2nd: Jan-Mar, 3rd: Apr-Jul |
A due date calculator provides a reliable estimate based on standard pregnancy duration. However, only 5% of babies arrive exactly on their due date. Most births occur within two weeks before or after the calculated date.
Yes, healthcare providers often adjust due dates based on early ultrasound measurements. These scans measure fetal size and development. Consequently, your due date may change during early pregnancy.
If you're unsure about your LMP, an ultrasound provides the most accurate dating. Early pregnancy scans measure fetal development to estimate gestational age. Always consult your doctor for the most precise due date.
For IVF pregnancies, calculate from the embryo transfer date instead of LMP. Add 266 days (38 weeks) to the transfer date. Alternatively, use your clinic's specific calculation method for accuracy.
Pregnancy is actually 10 lunar months (28 days each) totaling 280 days. Calendar months vary from 28-31 days, creating the apparent discrepancy. Therefore, 40 weeks equals approximately 9 calendar months.