The flag of Antigua and Barbuda has a ratio of 2:3. It consists of a red background with an inverted isosceles triangle in black, with its apex pointing towards the hoist side. Inside the triangle, there are three horizontal bands in blue, white and blue, respectively, with their widths in the ratios of 1:2:1. The color codes of the flag are:

• Red: Pantone 186 C; RGB 206, 17, 38
• Black: Pantone Black C; RGB 0, 0, 0
• Blue: Pantone 286 C; RGB 0, 51, 160
• White: RGB 255, 255, 255

The geometric properties of the flag are that the triangle's height spans half of the flag's height, while its base measures one-third of the flag's width. The blue stripes within the triangle each occupy one-quarter of the vertical space.

The flag was designed by Sir Reginald Samuel, a high school teacher, in 1966. It was adopted on February 27, 1967, when Antigua and Barbuda became independent from the United Kingdom.