How do you convert a GED to high school diploma?

You can't convert a GED to a high school diploma. They are different credentials. A GED (General Educational Development) is a test that demonstrates that you have the knowledge and skills equivalent to a high school graduate. A high school diploma is awarded upon completion of a high school's curriculum.

While a GED proves you have the knowledge, it doesn't provide the record of completing high school coursework. Colleges and employers will accept a GED as equivalent to a high school diploma for admission and employment purposes, but it's not the same thing. You cannot retroactively obtain a high school diploma after earning a GED.