. Sperm can live up to 72 hours once ejaculated. Sometimes the egg is found within 45 minutes for fertilization, while sometimes it can take as long as 12 hours. If the egg isn't yet released from the ovary, it is thought that the sperm can go into a holding pattern for about 24-48 hours while awaiting release of the egg.
The Laborious Journey of the Sperm
An average ejaculate discharges 40-150 million sperm which eagerly swim upstream toward the fallopian tubes on their mission to fertilize an egg. Fast-swimming sperm can reach the egg in a half an hour, while other may take days. The
sperm can live up to 48-72 hours. Only a few hundred will even come close to the egg, due to the many natural barriers and hurdles that exist in the female reproductive tract.
Conception Pictures Slideshow: The Amazing Journey From Egg to Embryo on MedicineNet.com