Ovulation Calculator

Understanding your fertile window

Your fertile window is the period when pregnancy is possible. It spans about 6 days: the 5 days before ovulation and the day of ovulation itself. Your egg can only be fertilized for 12–24 hours after release, but sperm can survive up to 5 days in the reproductive tract.

For a 28-day cycle, ovulation typically occurs around day 14. However, this varies significantly between women and even between cycles for the same woman.

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Understanding your ovulation cycle

Ovulation is the release of a mature egg from one of the ovaries. It is the key event that makes conception possible, and it happens roughly once per menstrual cycle. Most people with a 28-day cycle ovulate around day 14, counting from the first day of their period — but cycles vary widely. Our calculator estimates your ovulation date and fertile window based on the information you provide, giving you a clear picture of your most likely conception days.

What is the fertile window?

Sperm can survive in the female reproductive tract for up to five days after intercourse, while an egg remains viable for only 12–24 hours after ovulation. This means the fertile window — the days during which conception is possible — spans the five days before ovulation, the day of ovulation itself, and one day after: a total of about six days per cycle. The two days immediately before and on the day of ovulation are when the chance of pregnancy is highest.

How do I know when I am ovulating?

Several physical signs accompany ovulation. The most reliable is a change in cervical mucus: around ovulation, discharge becomes clear, stretchy, and resembles raw egg white — a texture often described as "EWCM" (egg-white cervical mucus). Basal body temperature (BBT) rises by about 0.2–0.5°C immediately after ovulation and stays elevated for the rest of the cycle. Many people also notice a one-sided pelvic ache called Mittelschmerz ("middle pain" in German) as the follicle releases the egg. Ovulation predictor kits (OPKs) detect the luteinising hormone (LH) surge that triggers ovulation, usually 24–36 hours before the egg is released.

What affects ovulation timing?

Stress, illness, significant changes in body weight, intense exercise, and certain medications can all delay or suppress ovulation. Conditions such as polycystic ovary syndrome (PCOS) cause irregular or absent ovulation in many people. Thyroid disorders and elevated prolactin levels can also disrupt the cycle. If your periods are very irregular — varying by more than a few days each month — tracking ovulation with OPKs or speaking to a doctor gives you more reliable information than a calculator alone.

Can you get pregnant outside the fertile window?

Technically, pregnancy requires intercourse within the six-day fertile window. However, because ovulation timing can shift unexpectedly — even in people with otherwise regular cycles — unprotected sex at any point in the cycle carries some risk of pregnancy. Our calculator provides estimates, not certainties. If you are trying to avoid pregnancy, use a reliable contraceptive method rather than relying on calendar-based calculations alone.

Trying to conceive: how often should we have sex?

Research suggests that having sex every one to two days throughout the fertile window gives the best chance of conception, rather than saving it for a single predicted "peak" day. Sperm quality can decline with too-frequent ejaculation (daily) or with very long gaps, so every other day is a practical and evidence-based approach. Trying for twelve months (or six months if over 35) without success is the standard threshold for seeking a fertility evaluation.