The flag of Spain, as it is defined in the Spanish Constitution of 1978, is divided into three horizontal stripes: red, yellow and red, the yellow stripe being twice the size of each red stripe. The state and war flags and ensigns must be charged with the Spanish coat of arms, while the civil flag and ensign leaves the inclusion of the coat of arms as optional. The coat of arms must be placed at one third the flag's length towards the hoist, and the height of the coat of arms should measure two fifths of the flag's width (i.e. hoist).
The current coat of arms was adopted on December 19, 1981, when it replaced the model of 1977 which, in turn, replaced the model of 1945, considered the official coat of arms of Francoist Spain. The coat of arms was the only changing element in those years. The colours previously defined in the constitution were amarillo (yellow) and rojo (red). Traditionally, the middle stripe was defined by the more archaic terms amarillo gualda (weld-coloured) but this word was removed from the draft of the Constitution by an amendment of Camilo José Cela, a writer appointed by the king to the Constituent Cortes. The origin of the current flag of Spain is the naval ensign of 1785, Pabellón de la Marina de Guerra under Carlos III of Spain.