What is the age of consent for a girl in SC, and what are the laws for 18 year old boy with 16 year old girl?

The age of consent in South Carolina is 16. If an 18 year old has consensual sex with a 16 year old, there would not be sexual offense criminal charges filed against him. There may have been other violations committed that were not sexual in nature, but this would depend on the circumstances.

SECTION 16-15-140. Committing or attempting lewd act upon child under sixteen.

It is unlawful for a person over the age of fourteen years to wilfully and lewdly commit or attempt a lewd or lascivious act upon or with the body, or its parts, of a child under the age of sixteen years, with the intent of arousing, appealing to, or gratifying the lust or passions or sexual desires of the person or of the child.

A person violating the provisions of this section is guilty of a felony and, upon conviction, must be fined in the discretion of the court or imprisoned not more than fifteen years, or both.

South Carolina statute makes it criminal to perpatrate sexual conduct on a minor under the age of 16; however,
SC Constitution Article III Legislative Department, SECTION 33. Age of consent. No unmarried woman shall legally consent to sexual intercourse who shall not have attained the age of fourteen years. (1999 Act No. 3, Section 1, eff February 16, 1999)