Pregnancy due date calculator
HealthEstimate the due date, conception date, current week and trimester from the last menstrual period.
Your results
Estimate due date and current week from the last period.
How the due date is estimated
We add 280 days (40 weeks) to the first day of the last menstrual period, which matches the standard Naegele's rule used by most clinicians.
Accuracy of the estimate
Only about 4% of babies are born on their estimated due date. Most arrive within two weeks before or after. Treat the result as a window, not a fixed day.
Frequently asked questions
Answers to the most common questions about this tool.
How is this result calculated?
It uses the method and inputs described on this page to provide an informational estimate.
How accurate is the result?
It is an estimate and should be interpreted as a guide, not an exact measurement.
When should I seek professional advice?
Seek qualified advice for symptoms, pregnancy, illness, medication use, or clinical decisions.
What information do I need to enter?
Enter current, accurate details and select the correct units before calculating.
What can affect this estimate?
Individual factors such as health, activity, body composition, and measurement technique can affect it.
Sources and methodology
Methodology: Estimated due date
Adds 280 days to the last menstrual period and estimates conception as 14 days later.
The date is indicative; ultrasound and clinical care may change it.
Last reviewed
July 15, 2026