Free Fertility Window Calculator
Calculate your most fertile days and peak fertility based on cycle length for conception planning.
days
days
Fertile Window Opens (Day)
9
Peak Fertility (Day)13
Ovulation Day14
Fertile Window Length6 days
Days Until Fertile Window1 days
Fertile Window Opens (Day) vs Days Since Last Period Started
Fertility Window
The fertile window is the 6-day period ending on the day of ovulation.
Ovulation Day = Cycle Length - 14 Fertile Window = Ovulation Day - 5 to Ovulation Day
Conception Probability by Day
Example Calculation
A 28-day cycle, currently on day 8.
- 01Ovulation = Day 14
- 02Fertile window = Day 9 to Day 14
- 03Peak fertility = Day 13
- 04Days until fertile window = 9 - 8 = 1 day
Frequently Asked Questions
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