Ovulationsrechner
The detailed guide below is currently available in English.
How the prediction works
The luteal phase — the stretch between ovulation and your next period — is fairly fixed at about 14 days for most people, while the first half of the cycle varies with cycle length. That is why the estimate subtracts 14 from your average cycle length: in a 28-day cycle, ovulation lands near day 14. The fertile window spans roughly the five days before ovulation plus the day after, because sperm survive up to five days while the egg is viable for about a day.
Getting better at reading your cycle
Calendar math is only a model. Ovulation predictor kits detect the luteinizing-hormone surge that precedes egg release; tracking basal body temperature confirms ovulation after it happens; and cervical mucus that turns clear and stretchy marks the fertile days directly. If your cycles swing widely month to month, calendar predictions will be loose — an ovulation kit or a chat with a gynecologist tells you more. This tool is informational and not a substitute for medical care.
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Can I get pregnant outside the fertile window?
Pregnancy from intercourse outside the six-day window is rare but not impossible, since cycle lengths and ovulation timing vary. If avoiding pregnancy is the goal, this calculator is not a safe method on its own — use dedicated contraception guidance from a clinician.
My cycles are irregular — will this work?
Partly. The tool accepts 21–42 day cycles, but irregular cycles often mean ovulation itself moves around, so treat the output as a rough sketch. Ovulation predictor kits, temperature tracking, or a medical workup give clearer answers for irregular patterns.