A 0.80 carat diamond is a medium-sized diamond that weighs 0.16 grams and measures approximately 6.0mm in diameter. The value of a 0.80 carat diamond is determined by its quality, which is determined by the four Cs: cut, color, clarity, and carat weight. A high-quality 0.80 carat diamond with excellent cut, color, and clarity can be quite valuable, while a lower quality diamond of the same weight may be more affordable. It's important to note that the size of a diamond is not the only factor that determines its value, and a smaller diamond with better quality may be more valuable than a larger diamond with lower quality. Therefore, it's important to consider all the factors that affect the quality and value of a diamond when making a purchase decision.