that your thumbs touch at the bottom to form a circle around the shoe. the right size is the one that you can leave a little gap at the top of the shoe.
you can also hold the bowl in front of your stretched arm for about 30 seconds. if you maintain a comfortable grip, then the shoes are of the right size for you. however, if you feel some pain or you start shaking, then the shoe may be oversized for you.
the bowls have a number and letter on the sides which indicate its weight. for instance, a 3m bowl is a size three bowl of medium weight, and a 