Since there is no specific situation or measurements for this, we just assume a circle with an arc BD. It has arbitrary values. In a circle, an arc can be measured by the measure of an arc. A measure of an arc is an angle that an arc makes at the center of a circle which it is a part. It has degrees units. It can be calculated when the length of an arc is given by using certain equations. The measure of an arc and the length of an arc always goes together.