It’s not an exact science, but you can expect to ovulate about 12-24 hours after a positive ovulation test. There are six days in the month that are considered your most fertile days. "The 'fertile window' for conception is defined as the five days leading up to the day of ovulation and is the time frame when the viability of both eggs and sperm should be maximal," says Dr. Thornton. "It is estimated that the fertilizable life of the human egg lasts up to 24 [hours] post ovulation and that sperm can survive up to five days in the reproductive tract. The majority of sperm is believed to survive 48-72 hours, which is why intercourse is most likely to result in pregnancy when it occurs within the three-day interval ending on the day of ovulation." Knowing how long sperm is believed to survive will help you understand when it's best to try to conceive. "This is also why a couple does not necessarily have to have intercourse on the actual day of ovulation to be able to conceive, but it needs to occur at some point in the fertile window," Dr. Thornton explains.