Free Ovulation Calculator
Estimate your ovulation day and fertile window based on your average cycle length, adjusted for cycles that differ from 28 days.
days
days
Ovulation Expected on Cycle Day
14
Fertile Window Starts Day9
Fertile Window Ends Day15
Days Until Ovulation4 days
Ovulation Expected on Cycle Day vs Days Since Period Started
Ovulation Timing
Ovulation typically occurs 14 days before the next period, not 14 days after the last one.
Ovulation Day = Cycle Length - 14
The fertile window spans from 5 days before ovulation through 1 day after, because sperm can survive up to 5 days and the egg lives about 24 hours.
Example Cycle Lengths
Example Calculation
A 28-day cycle, currently on day 10.
- 01Ovulation day = 28 - 14 = Day 14
- 02Fertile window = Day 9 to Day 15
- 03Days until ovulation = 14 - 10 = 4 days
Frequently Asked Questions
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