Overview

Calculate your estimated due date (EDD) based on the first day of your last menstrual period (LMP). This calculator uses Naegele's rule, the most widely used method in obstetrics, which assumes an average pregnancy duration of 280 days (40 weeks). This result is for reference only; please confirm your due date with your healthcare provider through ultrasound examination.

Formula

Estimated Due Date (EDD) = Last Menstrual Period (LMP) + 280 days

Naegele's Rule shortcut:
- Month: LMP month - 3 (add 12 if negative)
- Day: LMP day + 7
- Year: +1 year if month was adjusted, otherwise same year

How to Use

1. 1Select the first day of your last menstrual period (LMP).
2. 2Enter your average menstrual cycle length (default: 28 days).
3. 3Click the 'Calculate' button.
4. 4Your due date, current gestational age, and trimester information will be displayed.

Tips

• ✔If your cycle is not 28 days, an adjustment is needed. Longer cycles shift the due date later; shorter cycles shift it earlier.
• ✔For IVF pregnancies, the due date is calculated from the embryo transfer date — consult your fertility specialist.
• ✔About 80% of births occur within 2 weeks of the estimated due date.
• ✔If the ultrasound-based due date differs from the LMP-based date by more than 7 days, the ultrasound date takes priority.
• ✔This calculator does not replace medical advice. Always consult your obstetrician.

FAQ