Pregnancy Due Date Calculator
Enter the first day of your last menstrual period (LMP). We show an EDD by adding 280 days (40 weeks) and the common Naegele shortcut (LMP + 1 year − 3 months + 7 days).
Inputs
Results
EDD (+280 days from LMP)
How due dates are estimated
Obstetric dating often uses LMP assuming a 28-day cycle with ovulation around day 14 — individual cycles vary, and ultrasound dating may adjust the EDD. Treat these dates as planning aids; clinical dating trumps online tools.
Naegele’s rule matches adding 280 days for many calendar situations but can differ by 1 day from strict millisecond addition depending on month lengths — both are shown for transparency.
Medical care
Follow your doctor’s schedule — this page is educational only.
FAQ
Why two dates?
280-day addition and Naegele usually align closely; small differences come from calendar math.
What if cycles are long?
EDD from LMP alone may be early vs true conception — ultrasound is used to refine.