What this tool does
This calculator estimates your baby's due date using Naegele's rule, the standard method based on the first day of your last menstrual period. It gives the widely used 40-week estimate that helps you and your healthcare provider plan the months ahead.
How to use this tool
- Enter the first day of your last menstrual period.
- The calculator adds 280 days (40 weeks).
- Read your estimated due date.
- Confirm with your doctor or midwife, who may adjust it via ultrasound.
Why it matters
An estimated due date helps you plan appointments, leave and preparations. Only about one in twenty babies arrive exactly on the estimated date, so treat it as a guide. Always confirm with your healthcare provider — this tool is not medical advice.