A 1-carat diamond refers to a diamond that weighs exactly one carat, which is equivalent to 200 milligrams. Carat weight is one of the key factors in determining a diamond's value, along with its cut, color, and clarity. A 1-carat diamond is often considered a popular choice for engagement rings and other fine jewelry. The size of a 1-carat diamond can vary depending on its cut, but it typically measures about 6.5 millimeters in diameter. This size strikes a balance between being noticeable and elegant, making it a favored option for those looking to purchase a diamond without going to larger, more expensive weights.