The sizes numbers on today's frames are meaningless. What you need to compare is the head tube length or stack height of the frame and the TT length (with the proper correction for any difference in the seat tube angle) or the reach. For example, note that the XXL has a 20mm taller head tube than the XL. Although the TT on the XXL is 15mm longer, the reach is not 15mm longer, since the STA is a little less, at 72.5 degrees. That reduces the reach difference beween the two to only 10mm.

The proper size would either be an XL or XXL, but which one would depend on your body proportions and the type of fit that you desire. People of the same height can have much different leg and torso lengths, so posting your height is only on part of the story.

If you've been riding and know your saddle height, from the center of the crank to the top of the saddle, along the seat tube centerline, that would tell even more than your leg length.

http://www.gtbicycles.com/media/pdf/...atalog_GEO.pdf