Knobs attach to the cupboard at one point, whereas cabinet pulls attach at two points. You will find a huge selection of cabinet knobs at any hardware store. Knobs will range from 3/4 inch to 2 inches in diameter. If the knob is too small on a large cabinet, it will look out of place. The same goes for a large knob on a small cabinet. Besides the size of the cabinet door, there are a few other things to take into consideration when determining the size of the knob you will purchase.
Consider how hard it is to open the cabinet doors. New cabinets open quite easily whereas older cabinets tend to stick. Larger knobs are more accessible, making them easier to pull to open stuck cabinets.
Hold each knob you are considering for purchase to see how it feels in your hand. People with smaller hands tend to prefer grasping smaller knobs. If you have larger hands, it will be easier to hold onto larger knobs.
Measure your cabinet. Average cabinet size is 30 to 42 inches tall. If your cabinet is within the average size, select a knob 1 to 1 1/2 inches in diameter. If your cabinet is smaller, choose a smaller knob. If it is larger, select a larger knob.