1. Proposed in both U,S, House of Representatives and Senate, and passed by 2/3 majority vote. Then ratified by 3/4 of the states, with a 2/3 majority vote in each state legislature. All except the 21st amendment were done with this process.

2 Amendment is proposed by Congress by a two-thirds vote in both houses (House of Representatives and Senate), then ratified by special conventions in three-fourths of the States Only the 21st amendment was done this way

These two are possible, but neither have ever been used.

3 Amendment is proposed at a national convention when requested by two-thirds of the State legislatures , then ratified by three-fourths of the State legislatures

4 Amendment is proposed at a national convention called by Congress when requested by two-thirds of the State legislatures, then ratified by special conventions held in three-fourths of the States

Formal Amendment Method