What fraction of both houses of Congress must agree to approve a proposed amendment?

To amend the Constitution, a proposed amendment must be approved by a two-thirds majority in both the House of Representatives and the Senate. This requirement is established in Article V of the U.S. Constitution, which ensures that any alteration to this foundational document reflects a significant level of consensus among the nation's representatives. Securing two-thirds of the votes signifies a strong agreement across a diverse group of lawmakers, which helps to maintain the stability and integrity of the Constitution itself. This high threshold is intended to prevent arbitrary changes and ensures that only amendments with widespread support among elected officials are considered for ratification.