How are formal amendments to the constitution made

For a proposal it requires the approval of two-thirds of the two houses of Congress. For a ratification it is necessary a convention called by three-fourths of all state legislatures.

Explanation:

There are two types of amendments that can be made in the United States Constitution, the informal and formal.

The rules for the Formal method is in Article V, the process is divided in two-stage: proposal and ratification. For a proposal it requires the approval of two-thirds of the two houses of Congress. For a ratification it is necessary a convention called by three-fourths of all state legislatures.

“The Congress, whenever two thirds of both Houses shall deem it necessary, shall propose Amendments to this Constitution, or, on the Application of the Legislatures of two thirds of the several States, shall call a Convention for proposing Amendments, which, in either Case, shall be valid to all Intents and Purposes, as Part of this Constitution, when ratified by the Legislatures of three fourths of the several States, or by Conventions in three fourths thereof, as the one or the other Mode of Ratification may be proposed by the Congress […].”(Article V).