Our free Reverse Due Date Calculator helps you quickly determine your estimated conception date and last menstrual period (LMP). Simply input your baby's expected due date to work backwards and gain clarity on your early pregnancy timeline.
Formula:
The Reverse Due Date Calculator estimates key pregnancy dates based on a standard 280-day (40-week) gestation period from the Last Menstrual Period (LMP), or 266 days (38 weeks) from conception.
- Estimated Last Menstrual Period (LMP) = Expected Due Date - 280 Days
- Estimated Conception Date = Expected Due Date - 266 Days
Where:
- Expected Due Date: The anticipated date your baby will be born.