The flag of Iceland has an aspect ratio of 18:25. It consists of a blue field (Pantone 287 C) with a red (Pantone 186 C) Nordic cross that extends to the edges of the flag. The vertical bar of the cross is shifted towards the hoist side, and a white (Pantone White) fimbriation outlines the red cross.

Geometric properties and measurements:

1. The width of the blue field is equal to the flag's height (18 units).
2. The length of the blue field is equal to the flag's width (25 units).
3. The width of the red cross is 2 units.
4. The width of the white fimbriation is 1 unit.
5. The distance from the hoist edge to the center of the vertical bar of the cross is 7 units.

In summary, the flag's design can be described as a blue background with a red Nordic cross outlined in white, with dimensions in the ratio 18:25.