How is the due date calculated?
It adds 280 days (40 weeks) to the first day of your last menstrual period, known as Naegele's rule.
Health
Pregnancy Due Date Calculator
Enter the first day of your last period to get an estimated due date and current week of pregnancy.
Live calculator output
Enter the date of your last period to see the estimated due date.
How it works
The calculator uses Naegele's rule, the standard medical method for estimating due dates. It adds 280 days (40 weeks) to the first day of the last menstrual period (LMP). This assumes a 28-day cycle with ovulation on day 14. The result also shows your current pregnancy week and days remaining. While only about 5% of babies arrive on the exact due date, most births occur within two weeks of it.
Practical example
If your last period started on January 1, 2026, the estimated due date is October 8, 2026. If today is April 11, 2026, you are approximately 14 weeks and 2 days along, with about 180 days remaining.
Frequently asked questions
Reusable FAQ content keeps each calculator page richer for users and search engines.
Is this accurate?
It is an estimate. Only about 5% of babies are born on their due date. Ultrasound dating is more precise.
Does this replace a doctor visit?
No. Always confirm your due date with your healthcare provider.
What if my cycle is longer or shorter than 28 days?
If your cycle is regularly longer or shorter, the actual ovulation date shifts. Discuss cycle length with your provider for a more precise estimate.
What are the pregnancy trimesters?
First trimester: weeks 1-12. Second trimester: weeks 13-26. Third trimester: weeks 27-40. Each has distinct developmental milestones.
Related calculators
Cross-link adjacent tools to support navigation and future internal linking strategy.
Age Calculator
Measure age between two dates with a clean, readable breakdown.
Date Difference Calculator
Compare two dates and show both total days and calendar breakdown.
Sleep Calculator
Align your sleep schedule with natural 90-minute cycles.