The Constitution changes through a formal amendment process that requires overwhelming agreement across the country

The U.S. Constitution can be changed, but it is deliberately difficult. An amendment requires either two-thirds of both the House and Senate to propose it, or a constitutional convention called by two-thirds of state legislatures. After proposal, three-fourths of the states must ratify the amendment for it to become law. This high bar exists by design — the framers wanted to prevent hasty changes while still allowing the document to evolve.

Since 1789, only 27 amendments have been ratified. The first ten (the Bill of Rights) were added in 1791. The most recent was the 27th Amendment in 1992, which limited congressional pay raises. No amendment has been repealed except the 18th (Prohibition), which was undone by the 21st in 1933.

Key Takeaways

  • An amendment must be proposed by a two-thirds vote in both the House and Senate, or by a constitutional convention called by two-thirds of state legislatures.
  • After proposal, three-fourths of the states (38 out of 50) must ratify the amendment through their own legislatures or state conventions.
  • The ratification process has no time limit in most cases, so amendments can take years or decades to reach the required number of states.
  • Congress can set a deadline for ratification (typically seven years), but states can still vote to ratify after that deadline if Congress permits.

How an Amendment Gets Proposed in Congress

The most common path is a proposal from Congress. Any member of the House or Senate can introduce a joint resolution proposing an amendment. The proposal must then pass both chambers with a two-thirds supermajority — not a simple majority. This means at least 290 votes in the House (out of 435) and at least 67 votes in the Senate (out of 100).

Once an amendment passes Congress with the required two-thirds vote in both chambers, it goes to the states for ratification. Congress does not vote on it again. The proposal itself does not require the President's signature — amendments bypass the executive branch entirely.

Congress can also set a deadline for ratification, usually seven years from the date of proposal. However, this deadline is not absolute. States can still vote to ratify after the deadline if Congress votes to extend it or if Congress does not object. The 27th Amendment, for example, was ratified in 1992 — more than 200 years after it was proposed in 1789.

The Alternative: A Constitutional Convention

The second path to proposing an amendment is through a constitutional convention. This requires two-thirds of state legislatures (34 states) to call for a convention on a specific topic. Once 34 states have made the call, Congress must convene a national convention where delegates from each state gather to propose amendments.

A constitutional convention has never been held for this purpose. The only constitutional convention in U.S. history was in 1787, which created the original Constitution. Many legal scholars debate what would happen at a modern convention — whether it could propose amendments only on the called topic, or whether it could propose changes to any part of the Constitution. This uncertainty has made states hesitant to call for one.

If a convention did occur and proposed amendments, those proposals would still need to go through the same ratification process as congressional proposals: three-fourths of the states would have to approve them.

How States Ratify an Amendment

Once Congress proposes an amendment, it goes to the states. Each state legislature votes on whether to ratify it. For an amendment to become part of the Constitution, 38 out of 50 states must vote in favor. A state can vote yes, no, or take no action at all.

Most amendments are ratified by state legislatures. However, Congress can require that a state hold a special ratification convention instead, where delegates elected by voters decide whether to ratify. This has happened only once, for the 21st Amendment (repealing Prohibition) in 1933.

A state can change its mind. If a state votes to ratify an amendment and then later votes to reject it, the question of which vote counts has been debated by legal scholars. The safer assumption is that the first vote stands, but this has never been definitively settled by the courts.

How Long Ratification Takes

There is no set timeline for ratification. Some amendments have been ratified quickly — the 26th Amendment (lowering the voting age to 18) was ratified in just 107 days in 1971. Others have taken far longer. The 22nd Amendment (limiting presidents to two terms) took nearly four years, from 1947 to 1951.

The 27th Amendment shows the extreme end: it was proposed in 1789 but not ratified until 1992. During that 203-year span, states gradually voted to ratify it, and in the 1980s and 1990s, a push to ratify it gained momentum. Eventually, it reached the 38-state threshold.

Congress can set a seven-year deadline for ratification when it proposes an amendment. If an amendment does not reach 38 states within that window, it fails — unless Congress votes to extend the deadline. The 22nd Amendment had a seven-year deadline, but Congress extended it, allowing more states to ratify.

What Happens After Ratification

Once 38 states have ratified an amendment, it becomes part of the Constitution automatically. The Secretary of State certifies the ratification, and the amendment is added to the official text. No further action by Congress or the President is needed.

The amendment then becomes binding law across the entire country. Courts interpret it, and it can be enforced like any other part of the Constitution. If a state or individual violates the amendment, it can be challenged in court.

An amendment can only be changed or removed by another amendment. The 21st Amendment is the only one that repealed a previous amendment (the 18th). This underscores how permanent constitutional changes are meant to be.

Why the Process Is So Difficult

The framers designed the amendment process to be hard because they wanted the Constitution to be stable and not subject to passing political moods. A two-thirds supermajority in Congress means that a single party cannot unilaterally change the Constitution, even with a large majority. The requirement that three-fourths of states ratify means that smaller states and less populous regions have a say in whether the Constitution changes.

This difficulty is intentional. The Constitution has lasted over 230 years partly because it is not easy to alter. When change does happen, it reflects broad consensus rather than narrow political victory. The 27 amendments that have been ratified represent issues where a large majority of the country eventually agreed that the Constitution needed to change.

Frequently Asked Questions

Can the President veto an amendment?

No. The President has no role in the amendment process. Congress proposes amendments without the President's signature, and states ratify them without presidential involvement. This is one of the few areas of the Constitution where the executive branch has no power.

What if a state legislature changes and votes differently on an amendment?

Once a state votes to ratify an amendment, that vote is generally considered final. If a new legislature votes to reject it, the question of which vote counts is unsettled in law. However, the practical assumption is that the ratification stands, and the state cannot unratify an amendment.

How many amendments have failed to reach ratification?

Hundreds of amendments have been proposed in Congress, but only 27 have been ratified. Most proposed amendments never pass both chambers with a two-thirds vote. Of those that do pass Congress, many fail to gain ratification from 38 states. A few are still technically pending, including the 22nd Amendment's original seven-year deadline, which Congress extended.

Could an amendment be proposed that changes how amendments are made?

Yes. An amendment could theoretically change the two-thirds and three-fourths requirements, or create a new path to amending the Constitution. However, such an amendment would itself have to pass the current two-thirds and three-fourths thresholds, making it extremely difficult to lower the bar for future amendments.

What happens if 34 states call for a constitutional convention?

Congress would be required to convene a national convention. Delegates from each state would gather to propose amendments. However, the scope of the convention — whether it can only address the topic the states called for, or can propose changes to any part of the Constitution — is legally unclear and has never been tested.