Yes, how many carats should an engagement ring be can affect the size of the diamond. Generally, the higher the carat weight, the larger the diamond. However, the way the diamond is cut also plays a significant role in how it appears. A diamond with a perfect cut may look larger than a poorly cut diamond of the same carat weight. Know more about this here - https://ninetynineshine.com/blogs/news/how-many-carats-should-an-engagement-ring-be