Free tool · 05
Your fertile window, explained
See where the fertile window usually falls in a cycle like yours, and why every estimate has limits. No tracking, no saving, no reminders.
Private: nothing is saved or sent
- Period
- 09–13 Oct
- Likely fertile window
- ≈ 18–23 Oct
- Ovulation, estimated
- ≈ 23 Oct
- Next period, roughly
- 06 Nov
An estimate, not a prediction. Bodies don't keep calendars, and ovulation can shift from month to month.
Understand this
Why it's only an estimate
Ovulation usually happens 12 to 16 days before the next period, not on a fixed day of the cycle. The fertile window covers the five days before ovulation and the day itself, because sperm can survive for several days.
You don't need to time sex
Having sex every two to three days through the cycle covers the fertile window without needing to predict it, and takes some pressure off.
Irregular cycles
Irregular cycles are common and often harmless. Stress, illness, travel and conditions such as PCOS can all shift them. When cycles vary a lot, the window is harder to estimate, so this tool shows a wider band.
When to talk to a doctor
If cycles are often shorter than 21 or longer than 35 days, stop for three months or more, or are very painful, it's worth seeing a doctor.
Sources
- NICE. Fertility problems: assessment and treatment (CG156)
- Wilcox AJ, Weinberg CR, Baird DD. Timing of sexual intercourse in relation to ovulation. N Engl J Med, 1995
- NHS. Periods and fertility in the menstrual cycle
Reviewer
Dr Shesha Sinha
MBBS, MS (Obstetrics & Gynaecology)
Review pending
Please note
General information, not medical advice. This tool can't diagnose or predict outcomes. It runs in your browser: nothing you enter is saved or sent.
Severe pain, heavy bleeding or fainting? Call 112.
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