Less than 1 year. If a couple is having regular unprotected intercourse (2 or more times per week), there is an 80-90% chance of getting pregnant in one year. If you have been trying to conceive for over a year, you might consider seeing a fertility specialist to assess the problem.
Time to Conception. Normal fertile couples have a 20% pregnancy rate per month. If each month 20% conceive then after 12 months, about 92% should be pregnant. We find that about 10-13% of us couples will have a problem after a year so the math and reality are pretty close. See a fertility specialist if <35yrs and 12 mo or >= 35 yrs and 6 mo trying. You need to check for good timing. Infertility treatment successful.