Originally Posted by FBinNY

Normally, simply rolling the shape from flat to round wouldn't change the cross section.

So, it would be easy to use that to calculate* either thickness or width from the other.

EXAMPLE, if starting with a 2mm spoke, you'd have a cross section of 3.14mm (1x1xpi), or 3.14x1 or 2.5x1.25 when flattened. (or something comparable if more oval than flat)

I prefaced this by saying "normally" because it's possible to combine swaging and flattening to produce blades or ovals with smaller x-sections. (though offhand, I don't know of any that do)

*of course, if you have the spoke measuring is preferable.