The Star-Spangled Banner was originally 30 feet by 42 feet, or 9.1 meters by 12.8 meters. It weighed around 50 pounds and had 15 stripes, each 2 feet wide, and 15 stars, each about 2 feet in diameter. The flag was designed to be flown from a 90-foot flagpole and be visible from a great distance.
The storm flag that flew over Fort McHenry during the British attack on September 13, 1814, was 17 feet by 25 feet. The storm flag was used because heavy thunderstorms prevented the larger garrison flag from flying.
https://www.youtube.com/watch?v=aIbf6wB8LSU