How does a constitutional convention work?

To become part of the Constitution, an amendment must be ratified by either—as determined by Congress—the legislatures of three-fourths (presently 38) of the states or State ratifying conventions in three-fourths of the states. Thirty-three amendments to the United States Constitution have been approved by Congress and sent to the states for ratification. Twenty-seven of these amendments have been ratified and are now part of the Constitution. As of 2017, the convention process has never been used for proposing constitutional amendments.