Who determines and how do the electoral votes be given?

The total number of electoral votes is fixed at 538, which is the sum of the number of Senators (100) and Representatives (435), plus three for the District of Columbia (3).

Each state's electoral votes is calculated by adding their number of Senators (always 2) to their number of Congressmen in the US House of Representatives (at least one). The minimum number of votes is three; the current maximum is 55 (California).

Congressional Districts (representatives) for the US House of Representatives are apportioned to the states based on the size of each state's population as a percentage of the total US population, using the most recent census count.

The District of Columbia is an exception because it is federal territory (not a state), has no Senators and only one non-voting Representative in the House, but is still allowed the minimum three electoral votes.