Average size is 5.5 inches.

The people saying 12 inches are just liars.

1% of men worldwide have a penis measuring longer than 8¾ inches
3% of men worldwide have a penis measuring 7¾ to 8¾ inches
11% of men worldwide have a penis measuring 7 to 7¾ inches
19% of men worldwide have a penis measuring 6¼ to 7 inches
29% of men worldwide have a penis measuring 5½ to 6¼ inches
21% of men worldwide have a penis measuring 4¾ to 5½ inches
9% of men worldwide have a penis measuring 4 to 4¾ inches
4% of men worldwide have a penis measuring 3¼ to 4 inches
2% of men worldwide have a penis measuring 2¼ to 3¼ inches
1% of men worldwide have a penis measuring less than 2¼ inches