The flag of Gibraltar has an aspect ratio of 1:2, and consists of two horizontal stripes with the following color codes:

• The top stripe is 2/3 of the flag's width and is white (hex code: #FFFFFF)
• The bottom stripe is 1/3 of the flag's width and is red (hex code: #CE1126)

On the white stripe, there is a three-towered red castle whose height is equal to 2/5 of the total flag height. The castle's door and windows are also white. A gold key (hex code: #D0A978) hangs from the center tower; its length reaches the lower edge of the white stripe.

As for geometric properties and measurements:

• The castle's central tower is wider than the other two towers, and they all have rectangular bases.
• There is a small gap between each pair of towers.
• The key's shaft is straight with a circular bow, and the teeth on the bit extend both horizontally and vertically.