Pregnancy Due Date Calculator

It's the standard method obstetricians have used for generations to estimate a due date: add 280 days (40 weeks) to the first day of the last menstrual period (LMP) — it assumes a textbook 28-day cycle with ovulation occurring on day 14, which doesn't exactly match every individual's actual cycle.

It's a widely-used starting estimate, not a guarantee — only about 5% of babies are actually born on their exact calculated due date, and full-term birth is considered normal anywhere from 37 to 42 weeks. Healthcare providers often refine the estimate further using an early ultrasound, which can be more accurate than LMP-based dating alone, especially for people with irregular cycles.

Naegele's rule assumes a standard 28-day cycle; if your cycles are consistently longer or shorter, your actual due date may be earlier or later than this calculation suggests. Your healthcare provider can adjust for your specific cycle length or use ultrasound dating for more precision.

No — treat this as a convenient starting reference only. Always follow your healthcare provider's official due date, which accounts for ultrasound measurements and other clinical factors this simple calculation can't capture.