Conception Date Calculator
Estimate the likely conception dates based on your due date.
Understanding when you likely conceived can be a fascinating part of your pregnancy journey. Our Conception Date Calculator works backwards from your estimated due date to determine the most probable window of conception. Since a standard pregnancy lasts about 280 days (40 weeks) from the last menstrual period, conception typically occurs around two weeks after that period starts—during ovulation. This tool helps you pinpoint that magical window.
Due Date
Likely Conception Window
Frequently Asked Questions
The Science of Conception
Conception is not a single instant but a biological process. It requires the release of an egg (ovulation) and its fertilization by sperm. This calculator estimates your conception window based on the standard 40-week gestational calendar used by obstetricians.
1. The "Fertile Window" Explained
Timing is everything. Because sperm can survive inside the female reproductive tract for up to 5 days, and an egg survives for 12-24 hours after release, your "fertile window" is about 6 days long:
- Days 1-5 Before Ovulation: Sperm are waiting in the fallopian tubes.
- Day of Ovulation: The egg is released. This is peak fertility.
- 1 Day After Ovulation: The window closes rapidly as the egg dissolves if not fertilized.
2. Why is it an Estimate?
Medical due dates start counting from the Last Menstrual Period (LMP), assuming a 28-day cycle with ovulation on day 14. However, real life varies. Stress, illness, or natural cycle irregularities can shift ovulation. Therefore, the dates provided are a likely probability, not a certainty.
3. Conception vs. Gestational Age
It sounds strange, but when you are "4 weeks pregnant," the embryo has only existed for 2 weeks.
- Gestational Age: Counted from LMP. Used by doctors.
- Fetal Age: Counted from conception. Used by embryologists.
4. Frequently Asked Questions (FAQ)
Q: Can I conceive outside my fertile window?
No. Without an egg, conception is impossible. However, because estimating the window is difficult, it's possible to conceive on a day you thought was outside the window.
Q: Does date of conception affect due date accuracy?
If you know the exact date (e.g., IUI or IVF), your due date will be calculated from that day + 266 days, which is more accurate than the LMP method.