Health & Fitness
Due Date Calculator
Estimate pregnancy due date based on last menstrual period and cycle length.
Formulas and edge cases are reviewed against authoritative references before publication. For methodology, editorial standards, or corrections, use the links below.
Frequently asked questions
How is the due date calculated?
It uses a standard 40-week estimate adjusted by cycle length.
Is the due date exact?
No. It is an estimate and actual delivery may vary.
Can I use irregular cycles?
Use your best estimate for cycle length. Results may be less accurate.
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About this tool
This Due Date Calculator turns your inputs into practical results. Provide First day of last period and Cycle length to calculate Estimated due date and Weeks pregnant.
Adjust values to compare scenarios and see how sensitive the result is. The calculation uses the numbers as entered, so double-check units and expect small differences from rounding in the displayed totals.