Approximately how many days after sex does conception usually occur?

Depends: It depends on where you are in the cycle. If you have a 28 day cycle, you ovulate on cycle day 14, with cycle day 1 being the first day of your period. A day or two before ovulation, your cervical mucous thins, allowing sperm to travel up through the uterus to fertilize an egg in the tube. sperm can survive 2-3, maybe 4 days in good mucous. fertile days are generally cycle days 10-16