US shoe size is a system used to measure the size of shoes in the United States. It typically ranges from size 0 to size 20 for adults, with half sizes available for a more precise fit. The sizing is based on the length and width of the foot, ensuring comfort and support. The US shoe size system differs from other sizing systems, such as the UK shoe size and EU shoe size. Each system has its own scale, which can lead to confusion when purchasing shoes internationally. It's important to refer to size conversion charts when buying shoes from different regions.