Getting pregnant is, above all, a matter of timing since women are only able to conceive on the days on and around ovulation. Only when sperm and ova combine during a fairly short period, is there a change to get pregnant. The ovulation time and thus the fertile days therefore play an important role with respect to conceiving.

To make it easier for you to find out when your ovulation is, we offer you the ovulation calculator. By entering some information about your menstruation cycle, you can easily calculate your fertile days and thus the best days on which to conceive.

Calculating ovulation:

Please note: The fertility calendar calculates the fertile days according to a general formula. Using the fertility calendar as «contraception» is not recommended.

What information does the fertility calculator need?

1. First date of the last period

To calculate your ovulation as precisely as possible, you must know the first day of your last menstruation. The first day of the last period corresponds to the last day of your menstruation cycle. 

2. Cycle length in days

In addition to the first day of menstruation, the ovulation calculator needs the average length of your cycle. In general, this is 28 which corresponds to the period from the first day of menstruation to the day on which the next menstruation starts. Cycles vary from woman to woman and can be as long as 35 days. 

What information will I get from the ovulation calculator?

  • Next fertile days
  • Next ovulation date
  • Estimated birth date

Calculate average cycle length

The cycle length (if the cycle is regular) is calculated by determining the difference in days between the first day of one menstruation and the first day of the following menstruation. 

First date of the period May 1
First date of the period May 30 (next cycle) 

The first menstruation cycle ends on May 29, one day before the next period. 

The difference between May 1 to 29 is 29 days, i.e. the cycle is 29 days long. 

The length of the cycle varies from month to month in most women, so the average cycle length is calculated by averaging six cycle lengths. 

What is ovulation and when does it occur?

Ovulation is the time at which the woman’s mature ovum is released from the ovary and moves into the fallopian tube. During this period, the woman is fertile and can get pregnant. 

Ovulation usually occurs in the middle of the cycle, i.e. 14 days before the start of the next menstruation. The ovulation date can deviate from the norm as a result of hormonal fluctuations, stress or environmental changes. 

Ovulation explained briefly

When are the fertile days?

A woman’s fertile days are on and around the ovulation date and last approx. 6 days. They start 3-5 days before ovulation and end 12-24 hours after ovulation, whereby the probability of conception is the highest on the ovulation date. 

Calculate ovulation under special circumstances

Calculation with an irregular cycle length

Cycles vary from woman to woman. If a woman’s cycle lengths fluctuate significantly, the results of the ovulation calculator may not be accurate. The ovulation calculator can, however, assist in better narrow down the fertility period. 

Calculation without period

Illness, stress, cessation of the contraceptive pill as well as the period after pregnancy may result in a woman not having a period. This does not, however, mean there was no ovulation during the current cycle or that there will be no ovulation again during the next cycle.  

If you have a desire to have children and you cannot determine your cycle length or period on your own, we recommend consulting a gynaecologist. Ovulation can be determined accurately using ultrasound and blood analyses. 


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