Our ovulation calculator estimates when you’ll ovulate by counting back 14 days from the day you expect your next period. For instance, if your cycle is 28 days long, your next period should start 28 days from the first day of your last period.
Your fertile window includes the day you ovulate and the five days before. But keep in mind that you’re more likely to get pregnant during the last three days of this time frame. However, it is to be noted that counting back 14 days does not always apply as menstrual cycles can vary from woman to woman and month to month (the typical length of a cycle is anywhere between 21 and 35 days). Also, if you have irregular periods, it may become even more difficult to answer how to calculate ovulation as it might be tougher to pinpoint your fertile window.