How long after having unprotected sex can you take a pregnancy test and get accurate results?

Depends on ovulation: For home pregnancy tests you get in the drugstore, you usually must wait until you miss a period to get an accurate result. For a woman with a 28-day cycle, that means not earlier than about 14 days after ovulation. The length of time since ovulation is the key rather than the length of time since intercourse. You could try using an ovulation predictor kit to determine when you've ovulated.