Originally Posted by potemkin_city_limits
Does it actually matter which number you use to measure the leg opening? The fact that 9" flat = 18" around means that either number works.
To answer your weird and pointless question, when I take a pair of pants in to my tailor I tell her I want the hem to be 7.75" which she is free to either keep as 7.75" or delve into the extremely complex mathematical equivalent by simply multiplying by 2.
the issue which spawned his question was the op's statement that his leg opening was one inch too wide.
Whether we are talking about the flat across measurement or the actual circumference makes a big different when talking about how many inches too big it is.
Saying you want a 7.75 inch leg opening is obviously interpreted as the flat across measurement, but if you told your tailor to remove one inch, it is important to be on the same page about whether that inch will be taken from the circumference of the flat measurement.
Next time, give the question some thought before making an ass of yourself.