Actual Diamond Sizes of a 0.60 Carat Diamond
A typical round stone with a 0.60 carat size has a width of 5.5 mm; bear in mind that this can change if the cut is shallow or deep. The picture shows a ring which is US size 6; this is the same as an L 1/2 ring size in countries like Australia and Britain, and is an average ring size. The woman's hand shown in the picture has long and thin fingers - your fingers may or may not be similar - if your fingers are differently shaped, be aware that the ring you buy may present quite differently on your finger.
Also take into account the length and breadth of your fingers.
Look at the difference between the size of the woman's hand and the man's hand in the image - you can see that the woman's hand is much smaller and more petite (which is typical), so the diamond looks to be larger on her hand than it would appear to be on his.