List of Largest Empires - Measurement

Measurement

The calculation of the land area of a particular empire is controversial. In general, the list centers on the side of including any land area that was explored and explicitly claimed, even if the areas were populated very sparsely or not at all. For example, a large portion of Northern Siberia is included in the size of the Russian Empire but not the Mongol Empire. The Mongol Empire's northern border was somewhat ill-defined, but in most places it was simply the natural border between the steppe and the taiga. At the time the majority of the taiga and tundra were unexplored and uninhabited. This area was only very sparsely populated by the Russian Empire, but it had been explicitly claimed by the Russian Empire by the 17th century, and its extent had been entirely explored by the late 19th century. Similarly, the northernmost Canadian islands such as Ellesmere Island were explored and claimed by the British Empire by the mid-19th century (virtually the entire mainland was at least sparsely populated well before that).

Due to the historical trend of increasing population and GDP, the list of largest empires in these categories is highly dependent on which relatively recent political entities are defined as empires. The measures of population and GDP as a percentage of the world total take into account this historical growth, although decent GDP data is only available for the last few centuries, accurate only for the last decades.