By Josh Niccum
1. Propose An Amendment 
Either Congress or the States can propose an amendment ot the Constitution.
  • Both Houses of Congress must propose the amendment with a two-thirds vote. This is how all current amendments have been offered.
  • Two-thirds of the State legislatures must call on Congress to hold a Constitutional Convention.
2. Ratify An Admendment 
Regardless of how the amendment is proposed, it must be ratified by the States.
  • Three-fourths of the State legislatures must approve of the amendment proposed by Congress, or
  • Three-fourths of the states must approve the amendment via ratifying conventions. This method has only been used once, to repeal Prohibition (21st Amendment).
Is there a timeline for ratification? The US Supreme Court has held that ratification must happen within "some reasonable time after the proposal." Since the 18th Amendment, Congress has set a term of seven years for ratification. 

Only 33 amendments have received a two-thirds vote from both Houses of Congress. Of those, only 27 have been ratified by the States. Perhaps the most visible failure is the Equal Rights Amendment. 

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