Free ovulation calculator Calculate ovulation: Your fertile days at a glance

An ovulation calculator provides an estimate based on average values – nothing more. The rule of thumb ovulation ≈ cycle length minus 14 is correct on average, but your actual ovulation can deviate by several days: stress, lack of sleep, illness, travel or weight changes shift it. If you want to know more precisely, combine basal body temperature measurement and cervical mucus observation or use ovulation tests.

No – explicitly not. An ovulation calculator is not a method of contraception. Sperm survive for up to five days, ovulation can easily shift by days, and just a single incorrectly estimated cycle is enough for an unwanted pregnancy. If you want to use reliable contraception, talk to your gynecologist about suitable methods.

The days on which sexual intercourse can lead to pregnancy: about five days before ovulation until one day after. The reason for this length: sperm survive in the body for up to five days, while the egg itself is only capable of being fertilized for about 12 to 24 hours after ovulation. The highest probability is on the two days directly before ovulation.

Then the calculation becomes correspondingly more unreliable – it requires a reasonably constant cycle length. Use the average of your last three to six cycles as input. If your cycle fluctuates significantly or is permanently shorter than 21 or longer than 35 days, this should be discussed in a gynecological practice – especially if you are trying to conceive.

Some women feel what is known as Mittelschmerz – a pulling sensation in the lower abdomen around the time of ovulation. Physical signs such as stretchy, clear cervical mucus and the rise in basal body temperature after ovulation are more reliable. No single sign on its own is certain proof; it only becomes meaningful when combined over several cycles.

Ovulation tests measure the luteinizing hormone (LH) in the urine, which rises about 24 to 36 hours before ovulation. They are useful when trying to conceive to narrow down the fertile window more precisely than a calculator can. Start testing a few days before the mathematically expected ovulation – the calculator above helps you with this starting point.

The usual recommendation: If you are under 35 and have not become pregnant after twelve months of regular, unprotected intercourse, have it checked – from age 35, after just six months. Even before that: In the case of a missing period, very irregular cycles, or known pre-existing conditions, it is better to visit the gynecological practice sooner rather than later.

The fertilized egg usually implants in the lining of the uterus about 6 to 10 days after ovulation. Some women notice a light implantation bleeding or a pulling sensation, but most feel nothing at all. The calculator above shows you this calculated implantation window directly in the result – as a guide, not as an exact date.

The calculator adds 266 days to the calculated ovulation – that is how long a pregnancy lasts on average from fertilization. This is cycle-adapted and therefore more accurate than the classic Naegele's rule (last period + 280 days), which assumes a 28-day cycle. Nevertheless, the date remains an estimate: only about 4 out of 100 children are born exactly on the calculated day.

Weeks of pregnancy (SSW) are counted from the first day of your last period – not from conception. The notation 5+3 means: five full weeks plus three days. If your last period was in the past, the calculator above shows you the calculated week of pregnancy in the event that you had become pregnant in this cycle.

Nutrition can support a healthy cycle – it is not a miracle cure. A balanced foundation with sufficient energy, iron, folate, and omega-3 fatty acids is the basis; severe calorie deficits, on the other hand, can suppress ovulation. You can read about what specifically belongs on your plate during the ovulation phase in our article on nutrition around ovulation.