Medical & Pharmaceutical
Due Date Calculator
Calculate your estimated due date (EDD) based on your last menstrual period or conception date. Get a personalized pregnancy timeline with key milestones.
Enter your last menstrual period or conception date to calculate your due date
Related to Due Date Calculator
The due date calculator uses established medical guidelines to estimate your baby's expected delivery date (EDD). The calculation can be based on either your last menstrual period (LMP) or known conception date, using two scientifically validated methods:
Naegele's Rule (LMP Method)
When using the last menstrual period, the calculator adds 280 days (40 weeks) to your LMP date. This is the standard method used by healthcare providers worldwide. The calculation starts from the first day of your last period, which is considered week 1 of pregnancy, even though conception typically occurs around week 2.
Conception Date Method
If you know your conception date (from IVF, ovulation tracking, or other methods), the calculator adds 266 days (38 weeks) to this date. This method can provide a more accurate estimate but requires knowing the exact date of conception. It's particularly useful for those who have undergone fertility treatments or track ovulation closely.
Your due date calculation provides several key pieces of information to help you understand your pregnancy timeline:
Estimated Due Date (EDD)
Your EDD is when your baby is expected to arrive. It's important to note that only about 5% of babies are born exactly on their due date. Most births occur within two weeks before or after this date. The EDD serves as a guideline for monitoring your pregnancy's progress and planning prenatal care.
Conception Date
The conception date is when fertilization likely occurred. If using the LMP method, this is estimated at approximately 14 days after your last period. However, actual conception timing can vary based on your individual ovulation cycle and other factors.
Pregnancy Week and Trimester
Your current week of pregnancy and trimester help track fetal development and maternal changes. The three trimesters (weeks 1-13, 14-26, and 27-40) each bring distinct developmental milestones and physical changes. This information helps you and your healthcare provider monitor your pregnancy's progression.
1. How accurate is the due date calculation?
Due date calculations provide an estimate based on standard pregnancy duration. The accuracy depends on several factors, including the method used (LMP or conception date), the regularity of your menstrual cycle, and individual variations in pregnancy length. The conception date method tends to be more accurate when the exact date is known.
2. Why is pregnancy counted from the last period?
Pregnancy is traditionally counted from the first day of the last menstrual period because it provides a clear, identifiable date that most women can recall. This standardized approach, while adding approximately two weeks before actual conception, helps ensure consistent pregnancy dating across healthcare providers.
3. What can affect my actual delivery date?
Several factors can influence when you actually give birth, including: maternal age, previous pregnancies, family history, multiple pregnancies, medical conditions, and individual variations in pregnancy duration. Your healthcare provider may adjust your due date based on ultrasound measurements and other clinical factors.
4. When should I schedule my first prenatal visit?
Most healthcare providers recommend scheduling your first prenatal visit as soon as you know you're pregnant, typically between weeks 6-8 of pregnancy. However, if you have any pre-existing medical conditions, pregnancy complications, or other health concerns, you should contact your healthcare provider immediately.
5. What is the scientific source for this calculator?
This calculator implements Naegele's rule, the standard method for calculating pregnancy due dates endorsed by the American College of Obstetricians and Gynecologists (ACOG) and the World Health Organization (WHO). The calculations are based on extensive research validating the average pregnancy duration of 280 days (40 weeks) from LMP, or 266 days (38 weeks) from conception. This methodology is supported by numerous peer-reviewed studies in obstetric medicine, including research by the National Institute of Child Health and Human Development, and is consistently used in clinical practice worldwide. The calculator also incorporates modern adjustments for accurate conception dating when using assisted reproductive technologies.