Pregnancy Due Date Calculator
Naegele’s rule adds 280 days (40 weeks) to the first day of the last menstrual period. Actual delivery often happens across a window around that date. An ultrasound dating scan can adjust the estimate.
Estimated due date2026-10-22
Educational estimate only. Not medical advice.
Formula
Due date ≈ first day of last menstrual period + 280 days.
How to use this calculator
- Enter LMP as YYYY-MM-DD.
- Add 280 days.
- Confirm dates with your clinician.
Examples
Sample LMP
If LMP is 15 January, a 280-day estimate lands around 22 October the same year (non-leap variations apply).
FAQ
Why 280 days?+
It is the conventional 40-week obstetric dating from LMP, which already includes about two weeks before conception.
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