The size of flag is dependant on the size of the flagpole. For porch mount flagpoles the 3 x 5 Ft flag is the most common. For in-ground flagpoles the general rule of thumb is that the height of the flag should be 1/5th the height of the flagpole. For example take a 25 ft high pole – 1/5th of the 25 ft leaves 5 ft. So that would carry a 5 x 8 ft flag.
Please be aware of the size of flag that is recommended for your flagpole. Flying a larger flag than is recommended by the manufacturer may result in damage to the flagpole.
Common size range chart
15’ 3’x5’
20’ 3’x5’- 4’x6’
25’ 4’x6’ – 5’x8’
30’ 5’x8’ – 6’x10’
35’ 6’x10’ – 8’x12’
40’ 6’x10’ – 10’x15’
45’ 8’x12’ – 10’x15’
50’ 10’x15’ -12’x18’
60’ 10’x15’- 15’x25’
70’ 12’x18’ – 20’x 30’
80’ 15’x25’- 20’x38’
90’ 15’x25’ -20’x38’
100’ 15’x25’ -30’ X 60’