Does God ever actually say that premarital is sin?

Some people consider premarital to be adultery against your future spouse. I don't. They way I see it, in Biblical times people were getting married as soon as they were ually mature- 13 or 14 years old. Today, a lot of people wait until their 30's to get married. It's not realistic or even healthy to deprive yourself for that long. Of course, there are healthy and unhealthy ways to go about having , but I think evidence against premarital in the Bible is shady at best.