Enter values and select Calculate to see your result.
Estimated Delivery Date
This tool uses the common 280-day estimate from the first day of the last menstrual period. Actual delivery dates vary.
How to use the Pregnancy Due Date Calculator
Estimate a pregnancy due date from the first day of the last menstrual period.
- Enter first day of last period.
- Calculate estimated delivery date.
- Discuss differences with a healthcare professional.
Pregnancy Due Date Calculator formula
Estimated due date = last menstrual period + 280 days.
Worked example
Inputs: Last menstrual period January 1, 2026.
What to expect: Estimated due date is October 8, 2026.
How to read your result
Actual delivery can happen before or after the estimate; clinical dating may differ.
Frequently asked questions
Is 280 days exact?
No. It is a common estimate for a 28-day cycle.
Can I use it for care decisions?
Use it for general planning and follow clinician advice.