Pregnancy Due Date Calculator
Calculate your estimated due date based on your last menstrual period or conception date. Track pregnancy milestones.
How to Calculate
EDD = LMP + 280 days (Naegele's rule)
The estimated due date is calculated using Naegele's rule, which adds 280 days (40 weeks) to the first day of the last menstrual period. When using the conception date, 266 days (38 weeks) are added instead. Only about 5% of babies are born on their exact due date.
Frequently Asked Questions
How is the due date calculated?
The most common method is Naegele's rule: add 280 days (40 weeks) to the first day of your last menstrual period. Only about 5% of babies are born on their exact due date — most arrive within two weeks before or after.
How accurate is the due date?
Due dates are estimates. Only about 5% of babies arrive on their exact due date. Most are born between 38-42 weeks. Early ultrasound dating is more accurate than LMP-based calculations.
What are the three trimesters?
First trimester: weeks 1-12 (organ formation). Second trimester: weeks 13-27 (growth and development). Third trimester: weeks 28-40 (weight gain and maturation). Each trimester has distinct developmental milestones.