Own work. Geometry and dimensions from Government of Iceland — Icelandic National Flag and Act on of the National Flag of Icelanders and the Coat of Arms.

The regular National Flag of Icelanders shall be of sky-blue colour with a snow-white cross and a fiery-red cross within the white cross. The arms of the crosses extend to the edges of the flag and their width is 2/9 of the width of the flag and that of the red cross 1/9. The blue areas are rectangles; the blue hoist sections are square and the blue fly sections are the same width as the two squares, but twice as long. The proportion of the flag's width to its length is 18 to 25.

— Article 1 of the Flag Act No. 34/1944