Pregnancy Due Date Calculator
Estimate your due date from the first day of your last menstrual period.
How This Works
This uses Naegele's rule, the standard obstetric estimate: due date = first day of your last menstrual period + 280 days (40 weeks). It's an estimate based on averages, not a medical prediction — actual delivery timing varies and should be confirmed with your healthcare provider, especially if using ultrasound dating.
Formula
Example
A last menstrual period of January 1, 2026 gives an estimated due date of October 8, 2026.
Frequently Asked Questions
What is the due date for a last period starting June 12, 2026?
The estimated due date is March 19, 2027, using Naegele's rule (LMP + 280 days).
How many weeks pregnant does that make me today?
10 weeks and 0 days, in the first trimester.
Is this a medical prediction?
No — this is a standard estimate based on averages. Always confirm your due date and gestational age with your healthcare provider.