The national flag of Bangladesh (Bengali: বাংলাদেশের জাতীয় পতাকা) was adopted officially on 17 January 1972. It consists of a red disc on top of a green field, offset slightly toward the hoist so that it appears centred when the flag is flying. The red disc represents the sun rising over Bengal, and also the blood of those who died for the independence of Bangladesh. The green field stands for the lushness of the land of Bangladesh.
The flag is based on a similar flag used during the Bangladesh Liberation War of 1971, which had a yellow map of the country inside the red disc. In 1972 this map was deleted from the flag. One reason given was the difficulty for rendering the map correctly on both sides of the flag.
The first flag was designed by Student Leaders of Shawdhin Bangla Nucleus painter was Shib Narayan Das and was made from clothes donated by the owner of Apollo Tailors, Bazlur Rahman Lasker, of Dhaka's New Market. On 2 March 1971, the initial version of the flag was hoisted in Bangladesh for the first time at Dhaka University, as the Vice President of Dhaka University Students' Union (DUCSU), student leader A. S. M. Abdur Rab, raised the flag. The flag was conceived so as to exclude the crescent and the star considered as symbols of West Pakistan. According to CIA World Fact Book, the green used in the flag represent the lushness of the green landscape of the country. 
According to Bangladeshi government specifications, following is the specification of the national flag:
The flag will be in bottle green and rectangular in size in the proportion of 10:6, with a red circle in near middle.
The red circle will have a radius of one-fifth of the length of the flag. Its centre will be placed on the intersecting point of the perpendicular drawn from the nine-twentieth part of the length of the flag, and the horizontal line drawn through the middle of its width.
The green base of the flag will be of Procion Brilliant Green H-2RS 50 parts per 1000. The red circular part will be of Procion Brilliant Orange H-2RS 60 parts per 1000.
Depending on the size of the building the flag sizes will be 10 × 6 ft (3.0 × 1.8 m); 5 × 3 ft (1.5 × 0.91 m); 2.5 × 1.5 ft (760 × 460 mm). The size of the flag for car is 12.5 × 7.5 in (320 × 190 mm), and the size of the table flag for bilateral conferences is 10 × 6 in (250 × 150 mm).