House and Senate size and elections

The Congress meets in the United States Capitol in Washington, D.C. Both senators and representatives are chosen through direct election, though vacancies in the Senate may be filled by a governor appointment. Congress has 535 voting members: 435 representatives and 100 senators. 

The sitting of a congress is for a two-year term, presently beginning every other January; thus, the current congress is the 116th. Elections are held every even-numbered year on Election Day. The members of the House of Representatives are elected for the two-year term of a congress representing the people of a single constituency, known as a district. Congressional districts are apportioned to states by population using the United States Census results, provided that each state has at least one congressional representative. Each state, regardless of population or size, has two senators. Currently, there are 100 senators representing the 50 states. Each senator is elected at-large in their state for a six-year term, with terms staggered, so every two years approximately one-third of the Senate is up for election.