The menstrual cycle can be divided in two parts: the first is from the start of the menstrual period until the ovulation and the second is from the ovulation until the start of the next period. Different concentrations of hormones in the blood are characteristic for these periods. The length of the first period might vary, but the length of the second period is always fourteen days. Therefore, to calculate your ovulation day you have to subtract fourteen days from the expected start of your next period.

This might be difficult in women that have an irregular menstrual cycle length. The body temperature slightly rises when the ovulation starts in order to create a better environment for the incoming egg. You might want to measure your body temperature regularly and try to conceive when you notice an increase of about 0.5 degrees.


In the end, your gynecologist might be able to tell you according to an ultrasound scan the approximate day the ovulation might occur.