This list of the largest arch bridges ranks the world's arch bridges by the length of their main span. The length of the main span is the most common way to rank arch bridges. If one bridge has a longer span than another it does not necessarily mean that the bridge is longer from shore to shore or from anchorage to anchorage. The size of the main span may not always correlate with the engineering complexity involved in designing and constructing the bridge. However, the total length of bridges cannot be compared as there is no standard way to measure the total length of a bridge.