How are the total number of electoral votes in the electoral college determined?

The total number of electoral votes in the Electoral College is 538. It is determined by three parts, according to the Constitution Article II, Section 1, amended by the Twenty-third Amendment. The first number is the 435 in the US House of Representatives. The second number is the 100 in the US Senate. Third number is the three electoral college votes given Washington, D.C. by the Twenty-Third Amendment. The power to elect a president changes every ten years by the decennial census. The census is based on population, literally the people, and it changes power in the states as they change over time. The US Census of Population is not a count of citizenship, voting, history or militias. It is used to reapportion the number of each state delegation in the US House of Representatives, so at the same time, it changes the power to elect the President.