If you measure the total width of a cat's whiskers you will find that they are the same width as the cat's body.
Whiskers help a cat measure the width of an opening.
They tell the cat whether it can fit through an opening or not. The whiskers are extremely sensitive to touch and act as sensors to the environment as the cat ducks under bushes and undergrowth. The whiskers are part of a whole array of sensors that cover the cats whole body. If you look closely at a cats fur you will see some of the hairs are a little longer than the rest. These are called guard hairs.