1) after two-thirds of the House and Senate approve the proposal and send it to the states for a vote. Then, three-fourths of the states must approve the proposed amendment. (All 27 amendments have been ratified in this way)

2) a constitutional convention is called by two-thirds of the legislatures of the states. That convention can propose as many amendments as it deems necessary. Those amendments must be approved by three-fourths of the states