Purpose: Estimate your expected delivery date (EDD) from the first day of your last menstrual period using Naegele's rule (LMP + 280 days).
Due Date Calculator
The Due Date Calculator estimates your baby's arrival date (EDD) from your last menstrual period or conception date, and lays out a week-by-week pregnancy timeline.
Two ways to date it
From your last menstrual period, the due date is calculated as LMP + 280 days (Naegele's rule). From a known conception date, it is roughly 266 days later. The calculator supports both, and also shows current pregnancy week and trimester so you always know where you are.
How reliable is the date?
The EDD is a best estimate, not a deadline. Cycle length affects LMP-based dating, and an early ultrasound often adjusts it. Most babies are born within the two weeks either side of the estimate. Use it to plan appointments, leave, and preparation - and let your care provider's dating be the final word.
Frequently Asked Questions
How is the estimated due date calculated?
From the last period, it adds 280 days; from a known conception date, about 266 days. Both give an estimated delivery window.
Which is more accurate, LMP or ultrasound dating?
Early ultrasound dating is usually more accurate, especially with irregular cycles, and often refines the LMP-based estimate.
Does cycle length change the due date?
Yes. Longer or shorter cycles shift ovulation and therefore the LMP-based due date, so the calculator can factor cycle length in.
How many babies arrive on the due date?
Only about 1 in 20. Most births happen within two weeks before or after the estimated date.
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