Shape and Design

Flags are usually rectangular in shape (often in the ratio 2:3 or 3:5), but may be of any shape or size that is practical for flying, including square, triangular, or swallowtailed. A more unusual flag shape is that of the flag of Nepal, which is in the shape of two stacked triangles.

Many flag merchants prey on unwary buyers by offering incorrect flags, such as with the wrong proportions, crudely drawn, or one-sided. Some reference materials alter the flag proportions so they look uniform, such as decades of editions of the annual World Almanac and Book of Facts.
Many flags are dyed through and through to be inexpensive to manufacture, such that the reverse side is the mirror image of the obverse (front) side. This presents two possibilities:
If the design is symmetrical in an axis parallel to the flag pole, obverse and reverse will be identical despite the mirror-reversal.

If not, the obverse and reverse will present two variants of the same design, one with the hoist on the left, the other with the hoist on the right. This is very common and usually not disturbing if there is no text in the design.

Some complex flag designs are not intended for through and through implementation, requiring separate obverse and reverse sides if made correctly. In these cases there is a design element (usually text) which is not symmetric and should be read in the same direction, regardless of whether the hoist is to the viewer's left or right. These cases can be divided into two types:
The same (asymmetric) design may be duplicated on both sides. Such flags can be manufactured by creating two identical through and through flags and then sewing them back to back, though this can affect the resulting combination's responsiveness to the wind. Depictions of such flags may be marked with the symbol , indicating the reverse is congruent to (rather than a mirror image of) the obverse.

Rarely, the reverse design may differ, in whole or in part, from that of the obverse. Examples are the national flag of Paraguay, the flag of the U.S. state of Oregon, and the historical national flag of the Soviet Union. Depictions of such flags may be marked with the symbol .


Common designs on flags include crosses, stripes, and divisions of the surface, or field, into bands or quarters — patterns and principles mainly derived from heraldry. A heraldic coat of arms may also be flown as a banner of arms, as is done on both the state flag of Maryland and the flag of Kiribati.

The flag of Libya, which consists of a rectangular field of green, is the only national flag using a single color and no design or insignia.