America measures out to about 4,400-4,500 miles in length from its north coast to the southern tip. If we take Westeros to be 3,000 miles from the Wall to the south coast of Dorne, then that leaves roughly 1,500 miles of additional land north of the Wall to at least match the length of Westeros. The mapped portion of the continent (in the books and Lands of Ice and Fire) extends up to around 750 miles north of the Wall, which works quite well. The World of Ice and Fire map more than doubles this up to around 1,865 miles north of the Wall.

One curious new piece of information was unveiled by George R.R. Martin in 2013: he envisages the lands north of the Wall being roughly “thethe size of Canada. However, that’s not necessarily an issue as the landmass can continue and extend further into the opposite hemisphere. In addition, it may be that the WoIaF map is showing solely the geological landmass, whilst Martin was including the year-round pack ice in his size count (his planet presumably not undergoing the same degree as warming as our own, which is rapidly diminishing the amount of the Arctic which is frozen year-round). Presumably to the Others and their minions the distinction between continental bedrock and permanently frozen ice is academic.

These calculations allow us to draw the following conclusions:

Total length of Westeros from the North Pole to the coast of Dorne: 5084.06 miles

Distance from the Wall to the North Pole: 2,086.46 miles

Distance from the Wall to