The legal age of majority for contracts is 18 in most U.S. states. Reaching that age generally ends a person’s status as a minor and gives them full legal capacity to make binding agreements.
The rule developed as states moved away from the older common-law and statutory tradition that often treated 21 as the threshold for adulthood. The voting age was lowered nationally to 18 by the Twenty-sixth Amendment in 1971, and most states had already lowered or subsequently lowered their age of majority to match the modern concept of adult status.
This does not mean every 18-year-old can do everything associated with adulthood. Alcohol purchases remain restricted to 21 nationwide, and states set separate rules for driving, sexual consent, firearms, and other activities. Conversely, emancipation, marriage, or special statutes may give some minors contract-related powers earlier.
Another common mistake is treating a minor’s contract as automatically nonexistent. In many jurisdictions, contracts made by minors are generally voidable by the minor, subject to exceptions such as necessities and certain educational or employment arrangements. State law controls the details.