Quick answer: ovulation typically occurs about 14 days before your next period starts. Use our free Ovulation Calculator based on your last period date and cycle length.
How the Estimate Works
Given your average cycle length, the calculator counts back 14 days from your predicted next period to estimate ovulation, then identifies the fertile window — the several days before and including ovulation when conception is most likely.
Cycle Length Varies
Not everyone has a textbook 28-day cycle. Entering your actual average cycle length (which can range from about 21 to 35 days) gives a more accurate estimate than assuming the standard.
Frequently Asked Questions
How accurate is a calendar-based ovulation estimate?
It's a helpful estimate, but actual ovulation can vary cycle to cycle. Ovulation predictor kits or basal body temperature tracking add more precision.
What is the fertile window?
Roughly the 5-6 days ending on ovulation day, when sperm can survive long enough to fertilize a released egg.
Does irregular cycle length affect accuracy?
Yes, irregular cycles make calendar-based prediction less reliable; tracking multiple cycles or using additional methods helps.
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