How long after intercourse does conception take place?

Conception occurs within day or so of the sex. It takes about 3 weeks for the embryo to make enough HCG for a positive pregnancy test. Blood test may be done a day after a missed period. Home pregnancy tests should be done 4-5 days after the missed period. If the result is negative repeat the test in 4-5 days. Use first morning urine and follow instructions for the test carefully.

I think you want to know the window time after sex you can get pregnant. This window time will depend how long the sperms survive in your genital tract. In average, sperms survive up to 3 days and if there is an ovum released in that period, conception may occur. In rare cases, some sperms can survive up to 5 days.