Everything was fine until the day you had sex. You hope that it has worked, but who can really know? Well, this is where ovulation calculators come to help. To do that, however, you first need to make sure what your menstrual cycle length is – since not every woman’s cycles are exactly 28 days long(1), and even if they were, there can be slight deviations in between months due to stress or other factors (2).
The calculation of ovulation days starts with figuring out when in a month you got your period. For most women periods occur on a regular basis every 28 days +/- 7 days. Once you have established the first day of your last period(3), add 14 days to it –