Russia is not proportionately populated between the smaller western portion (almost 25%) of the country that is considered part of Europe, and the larger eastern portion (more than 75%) that is part of Asia. European Russia contains about 77% of the country's population (110,000,000 people out of about 144,000,000) in an area comprising almost 4 million km2 (1.54 million mi2); an average of 27.5 persons per km2 (70 per mi2). This territory makes up 38% of Europe. Its eastern border is defined by the Ural Mountains and in the south, it is defined by the border with Kazakhstan. This area includes Moscow and Saint Petersburg, the two largest cities in Russia.
The eastern portion of Russia, mostly Siberia, is part of Asia and makes up more than 75% of the territory with 22% of the country's population at 2.5 persons per km2 (6.5 per mi2).
European Russia Wikipedia
The term “European Russia” was used in the Russian Empire to refer to traditional East Slavic territories under Russian control, including what is now Belarus and most of Ukraine (Dnieper Ukraine).
Administrative districts (on a large scale called Federal Districts) do not exactly line up with European Russia, but they are decent approximations, depending on exactly how Europe is defined. There are two major trends, one to use administrative divisions north of the terminus of the Ural River, and one to draw an imaginary line from the Ural River, through the city of Yekaterinburg.
The following administrative districts are overwhelmingly European:
Sources: Population: Jan 1, 2015 Estimate, Federal State Statistics Service Russia (xls)
Notes:Sum of 6 Federal Districts does not account for the following:
Volga Federal District has 4 raions entirely in Asia, 1 mostly Asia, 1 bisected, 2 cities bisected, 1 settlement fully in Asia, which sum to 280,000 people and 30,000 km² in Asia (as defined by the Ural River)
Ural Federal District has roughly 200,000 people and 1,700 km² in Europe (West of the Ural River). If an imaginary line is extended from the end of the Ural River towards Yekaterinburg, where Europe/Asia divider signs exist, some very roughly 1.7 million people in the Federal District would be deemed "in Europe".
Similarly, the same imaginary line if straight, could include parts of very sparsely populated Northwestern Federal District, but this is commonly ignored.