Conception Date Calculator
Estimate your conception date based on your due date. Find out the likely window when conception occurred.
Enter Due Date
Conception Estimate
Estimated Conception Date
January 29, 2025
Fertile Window Start
Jan 24
Fertile Window End
Jan 30
Est. LMP Date
Jan 15
Gestation at Conception
~2 weeks
Understanding Conception Dates
Our conception calculator estimates when conception likely occurred by subtracting 266 days from your due date. This corresponds to approximately 2 weeks after the last menstrual period.
Important Notes
- Estimation only - Actual conception can vary by several days
- Sperm viability - Sperm can survive up to 5 days
- Ovulation varies - Not all cycles are exactly 28 days
Conception Calculator FAQ
How is the conception date calculated?▼
Conception typically occurs about 266 days (38 weeks) before the due date, or approximately 14 days after the first day of the last menstrual period. This is when ovulation most likely occurred.
Can I know the exact conception date?▼
The exact conception date is difficult to pinpoint because sperm can live for up to 5 days in the reproductive tract, and ovulation timing varies. The calculator provides an estimated window.
What is the conception window?▼
The fertile window spans about 6 days: the 5 days before ovulation and the day of ovulation itself. Conception is most likely during this period.