Pregnancy Due Date & Gestational Age Calculator
Estimate the due date and track pregnancy progress. Enter the first day of the last menstrual period to get the estimated due date (EDD), current gestational age, trimester, and days remaining.
Last menstrual period
Uses Naegele’s rule (LMP + 280 days), adjusted for cycle length.
Enter the first day of the last menstrual period.
For reference/education only — an ultrasound dating scan is more accurate, especially with irregular cycles. Calculated locally in your browser.
How it works
The estimated due date is the first day of your last period plus 280 days(40 weeks), a method called Naegele’s rule. Because it assumes ovulation on cycle day 14, we adjust for your average cycle length. A dating ultrasound in the first trimester remains the most accurate way to confirm.
Frequently asked questions
How is the due date calculated from LMP?+
Naegele's rule adds 280 days (40 weeks) to the first day of the last menstrual period. This tool also adjusts for cycle length (LMP + 280 days + (cycle − 28)).
How accurate is an LMP-based due date?+
It assumes a regular 28-day cycle with ovulation on day 14. For irregular cycles a first-trimester ultrasound dating scan is more accurate and often used to set the official due date.
What is gestational age?+
Gestational age is the time since the first day of the LMP, expressed in weeks and days. First trimester is up to 13 weeks 6 days, second 14–27 weeks, third from 28 weeks.
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