What is the proportion of the height and length of the flag?

Accorfing to usflsg.org the proportions of the US flag are width) of flag 1.0 length of flag 1.9 or, as a ratio, 10:19. This allows the flag to be made in any size from lapel pin to football field covering and still be "correct"Flag developers are very picky abut all aspects of the flag, the stars, stripes and blue field have their own aspect ratiOS. Even the colours are not just red, white and blue but:

• Old Glory Blue Pantone: 282C,
  
• Old Glory Red Pantone: 193C,
  
• White