Pregnancy Due Date Calculator
Calculate your estimated baby due date, current gestational age, and developmental trimesters based on your last menstrual period or conception date.
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How to Use Pregnancy Due Date Calculator
Pregnancy Due Date Calculator Formula / How It Works
The calculator calculates delivery dates using Naegele’s Rule, adding exactly 280 days (40 weeks) to the last period start date.
For example, let's look at a last menstrual period start date of October 1, 2025 and a cycle length of 28 days. By entering these values into the tool, you will get an estimated due date of July 8, 2026, with conception date projected around October 15, 2025 instantly.
Frequently Asked Questions
Only about 4% of babies are born on their exact due date; most arrive within a week before or after.
Pregnancy is timed as 40 weeks (280 days) starting from the first day of the last period.
The day the egg is fertilized, typically 14 days after your period starts in a 28-day cycle.
Because most women do not know their exact day of ovulation, whereas period start dates are easier to identify.
First trimester (weeks 1-12), Second trimester (weeks 13-26), Third trimester (weeks 27-40+).
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