Estimated Due Date (EDD) Calculator
Calculate your estimated due date (EDD) using Naegele's rule or conception date. Free pregnancy due date calculator with gestational tracking and trimester charts.
About This Calculator
The Estimated Due Date (EDD) Calculator helps expectant parents predict when their baby will be born. Using either Naegele's rule based on the first day of your last menstrual period (LMP) or the date of conception, our calculator provides an accurate estimated due date along with comprehensive pregnancy tracking information.
The calculator uses the standard medical formula: EDD = LMP + 280 days (40 weeks) for a 28-day cycle, with adjustments for different cycle lengths. For the conception method, we add 266 days (38 weeks) to the conception date, which corresponds to the actual fertilization date. This calculator follows the same methodology used by healthcare providers worldwide, as recommended by the American College of Obstetricians and Gynecologists (ACOG).
Understanding Your Results
Your estimated due date is a prediction - only about 4% of babies are born exactly on the calculated date. The due month range (EDD +/- 14 days) captures approximately 80% of all deliveries. The calculator also shows your current gestational age in weeks and days, which trimester you are in, and the percentage of pregnancy completed. These metrics help you track your pregnancy milestones and prepare for each stage.
Regional Notes
India: Pregnancy care in India typically follows LMP-based dating. The first antenatal visit usually occurs in the first trimester, where an ultrasound may adjust the due date. India's maternal healthcare guidelines recommend at least 4 antenatal visits during pregnancy.
United States: ACOG recommends first-trimester ultrasound for accurate dating. The due date may be adjusted if the ultrasound measurement differs by more than 7 days from LMP-based dating. Standard prenatal care includes 12-14 visits.
United Kingdom: The NHS offers a dating scan between 10-14 weeks to confirm the due date. The combined screening test for conditions like Down's syndrome is also performed during this scan. Standard prenatal care follows NICE guidelines with around 10 appointments.
Frequently Asked Questions
What is the estimated due date (EDD)?
The estimated due date (EDD) is the predicted date when labor may occur, calculated using Naegele's rule (adding 280 days to the first day of the last menstrual period) or by adding 266 days to the conception date. Only about 4% of babies are born exactly on the EDD, so it is considered an estimate rather than an exact prediction.
How is the due date calculated using Naegele's rule?
Naegele's rule calculates the due date by adding 280 days (40 weeks) to the first day of your last menstrual period (LMP). For cycle lengths different from 28 days, an adjustment is made by adding or subtracting the difference. For example, a 30-day cycle adds 2 extra days, while a 26-day cycle subtracts 2 days.
How accurate is the estimated due date?
The estimated due date is a prediction, not a guarantee. Only about 4% of babies are born exactly on the calculated due date. Approximately 80% of babies are born within a two-week window before or after the EDD, which is known as the due month. First-trimester ultrasound measurements provide the most accurate dating.
What is the difference between gestational age and fetal age?
Gestational age is calculated from the first day of the last menstrual period (LMP) and is approximately 40 weeks at term. Fetal age (or conception age) is calculated from the date of conception and is approximately 38 weeks at term. Gestational age is the standard used by healthcare providers worldwide.
How do I know my cycle length?
Your cycle length is the number of days from the first day of one period to the first day of the next period. The average is 28 days, but cycles ranging from 21 to 35 days are considered normal. Track your cycles for 2-3 months to determine your average. If you are unsure, our calculator uses 28 days as the default.
Can the due date change during pregnancy?
Yes, your due date can change during pregnancy, especially after an early ultrasound. First-trimester ultrasound measurements of crown-rump length provide the most accurate dating. If the ultrasound date differs significantly from the LMP-based date, healthcare providers may adjust the due date accordingly.
What is the due month range?
The due month range is a two-week window before and after the estimated due date. Since only about 4% of babies arrive exactly on the EDD, the due month (EDD +/- 14 days) captures approximately 80% of deliveries. Planning for this window helps expectant parents prepare for the arrival.