You might remember from high school sex ed that an egg can only survive for 12 to 24 hours after ovulation, while sperm can survive for 48 to 72 hours after sex. Unfortunately, this means that there’s a pretty narrow window of opportunity for babymaking.
To up your chances of timing things properly, it’s helpful to know when you ovulate. While you might have a vague notion that ovulation typically happens around day 14 of your menstrual cycle (counting the first day of your period as day 1), that is probably the case only for women with a regular 28-day cycle, which is a minority of us (most women fall somewhere in the 24- to 35-day range). What’s true on a broader scale is that ovulation usually occurs about 14 days before the last day of a woman’s menstrual cycle, or the day before she gets her period. So, for a woman with a 24-day cycle, ovulation likely happens around day 10, while a woman with a 35-day cycle would likely ovulate around day 21.
If you’re not sure how long your menstrual cycle is naturally or when you ovulate, it may be helpful to keep track on a calendar of when you get your period and how long it lasts, to give you a better sense of when you’re most likely ovulating. If you're feeling slightly more high tech, a Fertility Calculator can be a handy tool when time is of the essence.