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.
Frequently asked questions
Is the due date exact?
No. It is a population estimate from LMP. Only a small fraction of births occur on the predicted calendar day; clinicians refine dating with ultrasound.
Why do you show two similar dates?
The 280-day rule and Naegele calculation usually land close together; tiny differences come from month-length calendar adjustments in code.
What if my menstrual cycles are long or irregular?
LMP-based EDD can be early compared to true conception. Your provider may adjust using early scan measurements.
Should I stop other contraception based on this page?
No. Always follow medical guidance for fertility, contraception, and pregnancy confirmation.
Is my LMP stored on your servers?
No. The tool runs locally in your browser.