Advanced Ovulation Calculator using the Standard Days Method & Shettles Theory — backed by reproductive science research.
Enter your cycle details below to generate a personalized fertility calendar with your ovulation date, fertile window, and optimal conception timing.
Calculation Method:
Ovulation is estimated as Cycle Length - Luteal Phase days after your last period.
Your fertile window spans 5 days before ovulation through 1 day after.
Your next best chance to conceive is between:
Peak Ovulation Day:
Period Start
Fertile Window Opens
Ovulation Day
Next Period
Timing for Boy
Closer to ovulation may favor Y-sperm (faster, shorter-lived)
Timing for Girl
2-3 days before ovulation may favor X-sperm (slower, longer-lived)
Scientific Disclaimer: The Shettles Method is a theory, not scientifically proven. Current research shows no reliable method to influence biological sex through timing of intercourse. Natural conception results in approximately 50/50 odds regardless of timing.
Understanding the phases of your menstrual cycle is key to identifying your fertile window. Here's what happens during each phase.
| Phase Name | Days (Avg 28-day cycle) | Hormone Focus | What's Happening | Fertility Level |
|---|---|---|---|---|
|
Menstruation
|
Days 1-5 | Estrogen & Progesterone Low | Uterine lining sheds; period bleeding occurs | Low |
|
Follicular Phase
|
Days 6-11 | Estrogen Rising | Follicles develop in ovaries; egg matures; uterine lining rebuilds | Low-Medium |
|
Fertile Window
|
Days 12-16 | Estrogen Peak → LH Surge | Cervical mucus becomes egg-white consistency; sperm can survive 3-5 days | High |
|
Ovulation
|
Day 14 (±2 days) | LH Surge Triggers Release | Mature egg released from ovary; egg viable for 12-24 hours | Peak |
|
Luteal Phase
|
Days 15-28 | Progesterone Dominant | Corpus luteum produces progesterone; uterine lining thickens for potential implantation | Low |
Developed by Georgetown University's Institute for Reproductive Health, this method identifies days 8-19 as fertile for women with cycles between 26-32 days. Our calculator adapts this for all cycle lengths.
Sperm can survive in the female reproductive tract for 3-5 days under optimal conditions. This is why the fertile window extends before ovulation, not just on the day itself.
Once released, an egg is viable for fertilization for only 12-24 hours. This is why timing intercourse in the days leading up to ovulation is often more effective than waiting for ovulation day.
Evidence-based articles to help you understand your body and optimize your conception journey.
Learn how to track your BBT to confirm ovulation, identify your luteal phase length, and detect early pregnancy signs with precision.
Read Full GuideDiscover the science-backed "fertility diet" including folate-rich foods, omega-3s, antioxidants, and nutrients that support reproductive health.
Read Full GuideLearn to recognize cervical mucus changes, mittelschmerz (ovulation pain), breast tenderness, and other natural fertility indicators.
Read Full GuideOur suite of free calculators supports every stage of your conception journey.
Estimate your baby's arrival date from LMP or conception.
✨Predict when implantation may occur after conception.
🧪Find the optimal day to take a test for accurate results.
💕Work backward from due date to estimate conception.
Our calculations and educational content are informed by leading reproductive health organizations.