The size of a flag patch can vary depending on its intended use and the specific design or country it represents. Flag patches are commonly found in various sizes, typically ranging from around 2 inches by 3 inches (5 cm by 7.5 cm) to 3 inches by 4.5 inches (7.5 cm by 11.5 cm). However, there is no standard size for flag patches, and larger or smaller patches can also be available depending on the supplier or manufacturer.