Ovulation & Fertility Calculator (Cycle Tracker)
Track your ovulation and fertile window with our free Ovulation & Fertility Calculator. Enter the first day of your last period and your average cycle length to get your ovulation date, fertile window, and next period date. Plan your pregnancy or track your cycle with confidence using this easy-to-use tool.
Ovulation & Fertility Calculator
Your Ovulation Results
What This Means
Complete the form and click "Calculate Ovulation" to see personalized insights about your cycle and fertility.
How to Use the Tool
1. Enter LMP
First day of your last period.
2. Set cycle length
Your average cycle length in days.
3. Get insights
Ovulation date, fertile window & calendar.
How It's Calculated
Key Formulas
- Ovulation Day: Cycle Length − 14
- Fertile Window: Ovulation − 5 to Ovulation
- Next Period: LMP + Cycle Length
- Due Date: Ovulation + 266 days
Cycle Phases
- Menstrual Phase: Days 1–5
- Follicular Phase: Days 6–13
- Ovulation: Day ~14
- Luteal Phase: Days 15–28
About Ovulation & Fertility
What is Ovulation?
Ovulation is the release of a mature egg from the ovary. It typically occurs around day 14 of a 28-day cycle. The egg is viable for about 12–24 hours after release. Your fertile window is the 5 days leading up to ovulation and the day of ovulation itself — this is when conception is most likely to occur.
Key Facts:
- Fertile Window: 5 days before ovulation + ovulation day
- Sperm Survival: Up to 5 days in the female reproductive tract
- Egg Survival: 12–24 hours after ovulation
- Best Time to Conceive: 1–2 days before ovulation
Limitations of This Tool
- Assumes a regular cycle length — irregular cycles may affect accuracy.
- Does not account for ovulation variability or lifestyle factors.
- Not a substitute for medical advice or fertility diagnosis.
- Ovulation prediction is based on a standard 14-day luteal phase — individual variations exist.
Trust & Privacy
Your data stays in your browser. All calculations happen locally. We never send your data to any server.
No registration or login required. Your privacy is 100% protected.
Uses standard fertility tracking methods. Our tool follows established reproductive health principles.
No cookies used for tracking. Your history is stored locally in your browser's localStorage.
Real-World Examples
LMP: Jan 1, Cycle: 28 days
Ovulation: Jan 14
LMP: Mar 15, Cycle: 32 days
Ovulation: Mar 29
LMP: Jun 1, Cycle: 26 days
Ovulation: Jun 12
Frequently Asked Questions
References
- American College of Obstetricians and Gynecologists. Fertility Awareness Methods. acog.org
- World Health Organization. Reproductive Health. who.int
- National Institutes of Health. Fertility and Ovulation. nichd.nih.gov