In Utah, the age of legal majority, or adulthood, is 18 years old. After then, you can marry, buy cigarettes, and engage in a variety of other adult activities other from purchasing alcohol. The only thing you cannot do is vote in an election. The first thing you should know about what can I do at 18 in Utah is that the law defines adulthood as reaching the age of 18 years. This means that anyone who claims to be an adult by another definition is lying. For example, someone could say they're an adult because they've reached the age of 25 without having been born yet, or when they turn 19 in December. These people are not adults according to the law, even though many other things may link them to being an adult. For example, if they had a driver's license or passport, they would be considered adults under the law. The second thing you need to know is that in Utah, there is no such thing as "adult supervision". If you want to make sure someone does what they are supposed to, like go to school or work, you have to trust them to choose how they live their lives after they reach the age of 18. No one can stop you from teaching an older sibling or friend how to drive, for example, even if they go on to become an alcoholic or drug addict.