Article I, Section 5 of the Constitution requires "a Majority of each [House] shall constitute a Quorum to do Business," meaning at least 218 House members (when there are no vacancies) and 51 senators must be present to vote on legislation. The Constitution lets a smaller number adjourn from day to day and compel absent members'' attendance "in such Manner, and under such Penalties as each House may provide." In practice, Congress presumes a quorum is present unless a member demands a quorum call, forcing the clerk to count how many members are actually in the chamber. Members present but not voting still count toward the quorum. Each chamber sets its own rules for determining quorum because the Constitution does not prescribe the method. The quorum requirement stops small factions from passing laws when most members are absent, though it does not require that a majority actually vote on each bill, only that a majority be available to vote if they choose.