Fertility Window Calculator
Pregnancy isn't just about one day. It's about a 6-day window where sperm viability meets ovulation. Identify your "High Probability" days to maximize your chances.
6-Day Window
Full conception range
Peak Day
Highest chance
Sperm Survival
5-day viability logic
Intercourse Plan
Recommended timing
What is the Fertile Window?
It is the period during the menstrual cycle when it is biologically possible for a woman to conceive. It consists of the 5 days *before* ovulation and the day of ovulation itself.
Egg vs. Sperm Lifespan
The key to understanding this window is lifespan. An egg only survives for 12-24 hours after release. However, sperm can survive in the female reproductive tract for up to 5 days in fertile cervical mucus.
The "Waiting Game"
The goal is to have sperm waiting in the fallopian tubes *before* the egg is released.
Peak Fertility
The chances of conception are highest 1-2 days before ovulation, not necessarily on the day of.
Closing the Window
24 hours after ovulation, the egg dissolves and the window closes until the next cycle.
Next 3 Cycles
We calculate windows for your next three periods so you can plan months in advance.
Symptom Check
Learn what physical signs (Temperature, Mucus) typically appear during these specific days.
Timing Advice
Get recommendations on frequency of intercourse (daily vs. every other day) during the window.
Why Use This Tool?
Focus on Viability
Unlike basic period trackers, we emphasize the sperm survival window, giving you more opportunities to try.
Clear Probability
We mark days as "Low", "High", and "Peak" fertility so you know where to focus your energy.
No Login Required
Instant results without creating an account or sharing personal health data.
Find Your Fertile Window
Enter your cycle details below.
How to Use the Fertility Calculator
Plan your parenthood journey in 3 steps.
Enter Period Date
Select the first day of your most recent period. This helps us anchor the timeline.
Input Cycle Length
Provide the average number of days between periods. If unsure, use 28 days (the average).
See Your Window
The calculator highlights the 6 specific days where intercourse is most likely to lead to conception.
Odds of Conception by Day
Not every fertile day is equal. Here is the statistical breakdown.
Tips for Success
Timing is Key
Don't wait for ovulation day. Start having intercourse every other day once your fertile window opens (5 days before).
Healthy Habits
Both partners should limit alcohol, stop smoking, and take prenatal vitamins (folic acid) to improve egg/sperm quality.
Track Signs
Look for clear, stretchy cervical mucus (like raw egg whites). This is a biological sign that your window is open.
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Frequently Asked Questions
Can I get pregnant after ovulation?
It is highly unlikely. Once the egg dissolves (12-24 hours after release), conception cannot occur until the next cycle. This is why timing *before* ovulation is crucial.
What if my cycle varies?
If your cycle varies by more than a few days (e.g., 26 days one month, 32 the next), use the shortest cycle length to ensure you don't miss the start of your window. Ovulation kits can also help.
How often should we have intercourse?
Every day or every other day during the 6-day window is recommended. Every other day is often sufficient to maintain sperm count while ensuring sperm is present when the egg releases.
Does age affect the window?
The window length remains the same, but the likelihood of conception decreases with age as egg quality and quantity decline.