If you are not on hormonal birth control such as the NuvaRing or the Pill, it's generally believed that all women ovulate on day 14 of their menstrual cycle. So if you got your period on the first of the month, you would ovulate 14 days later, on day 15. This rule is not necessarily correct for all women, and is based on the assumption that a woman's body follows a perfect 28-day cycle. 
