Find your fertile window and ovulation date
🩺 Understanding Your Cycle The average menstrual cycle is 28 days, but can range from 21-35 days. Ovulation typically occurs 14 days before your next period starts. Your fertile window includes the 5 days leading up to ovulation and the day of ovulation itself.
A person is typically born with all the eggs they'll ever have — around 1-2 million at birth — but only about 300 to 400 will actually be released through ovulation over a reproductive lifetime.
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What is Ovulation? Ovulation is the point in the menstrual cycle when an ovary releases a mature egg. It usually happens about 14 days before your next period begins. Once released, the egg can be fertilized for roughly 12 to 24 hours; if it isn't, the cycle ends with menstruation and the process starts again.
The Fertile Window: The fertile window spans about six days — the five days leading up to ovulation plus ovulation day itself. This is because sperm can survive in the reproductive tract for up to five days, while the egg is viable for only about a day. Timing intercourse within this window gives the best chance of conception.
How It's Calculated: This calculator uses the calendar method. It estimates your next period from your cycle length, places ovulation roughly 14 days before that date, and then marks the five-day fertile window that precedes it. The approach works best for people with regular, predictable cycles.
Accuracy & Limitations: The calendar method is an estimate, not a precise prediction. Cycle length naturally varies from month to month, and stress, illness, travel, or hormonal changes can shift the timing of ovulation. Irregular cycles reduce accuracy further. Ovulation predictor kits, basal body temperature charting, and cervical-mucus tracking give more precise, personalized signals.
Important: This tool is for general information and family planning only. It is not medical advice and is not a reliable method of contraception. If you are trying to conceive, having difficulty conceiving, or seeking birth control, speak with a doctor or other qualified healthcare provider for guidance tailored to you.
Example: Say your last period started on the 1st, with a 28-day cycle. Your next period is expected around the 29th. Ovulation falls 14 days before that — around the 15th — and your fertile window runs from the 10th through the 15th.
This calculator uses the calendar method: it estimates your next period from your cycle length, places ovulation roughly 14 days before that date, and marks the five-day fertile window that precedes it.
About six days — the five days leading up to ovulation plus ovulation day itself — because sperm can survive up to five days while the egg is viable for only about a day.
No — this tool is for general information and family planning only. It is not medical advice and is not a reliable method of contraception. Speak with a healthcare provider for guidance tailored to you.