The Flag of England is the St George's Cross. The red cross appeared as an emblem of England during the Middle Ages and the Crusades and is one of the earliest known emblems representing England. It achieved status as the national flag of England during the 16th century.

Saint George became the patron saint of England in the 13th century, and the legend of Saint George slaying a dragon dates from the 12th century.

The proportions of the flag are that the red cross has a width of 1/5 of the height of the flag.

(Wikipedia)