Bridge scour is the soil erosion caused by water flowing around bridge supports. Research has shown that scour has been the number one cause of bridge failure in the United States with an average annual rate of 22 bridges collapsing or being closed due to severe deformation. In this paper, the authors aimed to quantify the bridge scour risk in order to help people understand how risky the bridge scour is. The widely accepted definition of risk was adopted in the paper, the probability of failure times the value of the consequence. First, the NYSDOT Bridge Failure database and FDOT Unknown Foundation Bridges Database were used to quantify the bridge scour risk. Second, several other societal risks, including cancer, car accidents, and plane crashes, were analyzed to be comparable to bridge scour risk. Finally, the authors proposed the acceptable risk level, medium risk level, and unacceptable risk level in the United States based on the analyses in the paper. The outcome of this paper will aid people or authorities in understanding the risk of bridge failure as well as other society risks.