The flag of Switzerland consists of a red square with a bold, equilateral white cross in the centre. It is one of only two square sovereign-state flags, the other being the flag of the Vatican City. (The civil and state ensign, used by Swiss ships and boats, has more traditional proportions of 2:3).
Only the dimensions of the cross are formally established since 1889: "The coat of arms of the federation is, within a red field, an upright white cross, whose [four] arms of equal length are a sixth longer than their width.". The size of the cross in relation to the field is not formally established except on the naval ensign. A relation of 2:3 or 7:10 to the span of the flag is usual.
The Red Cross symbol used by the International Committee of the Red Cross is based on the Swiss flag. The Red Cross on a white background was the original protection symbol declared at the 1864 Geneva Convention. It is, in terms of its colour, a reversal of the Swiss national flag, a meaning which was adopted to honour Swiss native and Red Cross founder Henry Dunant.
The short-lived Free State of Icaria proclaimed in 1912 in the Greek island of that name, used a flag similar in shape to the Swiss civil and state ensign, except for being blue rather than red.