Due Date Calculator
Estimate your pregnancy due date and current week from your last menstrual period or conception date.
Enter the first day of your last period to estimate your due date.
Estimated using Naegele's rule (280 days from your last period, adjusted for cycle length). This is an estimate for general information only — your healthcare provider's estimate based on an ultrasound is more accurate.
How the Due Date Calculator works
Enter the first day of your last menstrual period and your average cycle length. The calculator applies Naegele's rule — adding 280 days, adjusted for a cycle length other than 28 days — to estimate your due date, current week of pregnancy, and likely ovulation date.
Frequently asked questions
What is Naegele's rule?
A standard method for estimating a due date: adding 280 days (40 weeks) to the first day of your last menstrual period, assuming a typical 28-day cycle.
How accurate is this estimate?
Only about 5% of babies are born on their exact estimated due date — it's a useful planning estimate, and most babies arrive within about two weeks of it either way.
Why does cycle length matter?
A longer or shorter cycle shifts when ovulation (and conception) likely occurred relative to your last period, so the calculator adjusts the due date accordingly.