Congress cannot amend the US Constitution on its own authority. A 2/3 vote by both houses may authorize that a proposed amendment be sent to the states for ratification. If 3/4 of the states ratify the amendment it becomes effective.
2/3
2/3
Two-thirds
2/3
To approve a proposed amendment to the U.S. Constitution, a two-thirds majority is required in both houses of Congress. This means that at least 67 out of 100 senators and at least 290 out of 435 representatives must vote in favor of the amendment. Once this threshold is met, the amendment can then be sent to the states for ratification.
two-thirds
Three-fourths of state legislatures must approve an amendment proposed by Congress to the United States Constitution. An alternate method of ratification is for three-fourths of states must vote in favor of the amendment during a ratifying convention. This alternate method has only been used one time, for the ratification of the Twenty-First Amendment which repealed Prohibition.
Two-thirds
51%
Three fourths.
Not only Congress needs to approve a change, but the states must also approve.
To ratify a new amendment, the proposed amendment has to be approved by 2/3 of both houses of congress before it is approved by 3/4 of the state legislatures or by 3/4 of the states in special conventions convened specifically to debate and decide on the proposal