ps you can try to use this new incredible free prog on line!
from your original to maxi 2880 * 2880
http://rsizr.com/
how to http://help.rsizr.com/

Another thing about prints : if your original image has "jaggie" : resolution is nothing only pixels is important!
in photoshop or other : "progressive outline" 4*4 pixels and cross over the image for erase "jaggies"
with a 4096*4096 you can make prints 4 * 3 meters without any problem ! (if you have erased jaggies)
so with 2880 * 2880 you can make something like 2 * 2 meters :)