The flag of Guernsey has an aspect ratio of 2:3. It consists of a white field with a red St. George's Cross, and in the upper left quadrant, there is a smaller yellow cross with arms that are indented at the ends, known as a cross patée.

Color codes:

• Red (St. George's Cross): Pantone 186 C, HEX #C8102E, RGB (200,16,46)
• Yellow (Cross Patée): Pantone 116 C, HEX #FFCD00, RGB (255,205,0)

Geometric properties:

• The width of each arm of the St. George's Cross is 1/10th of the flag's height.
• The cross patée's width is 1/5th of the flag's height, and its length is 1/5th of the flag's width.

Measurements:

• For a flag with a width of 180 cm, the height would be 120 cm.
• The width of each arm of the St. George's Cross would be 12 cm.
• The cross patée would measure 24 cm by 36 cm.