If you mean for a constitutional convention to propose amendments(s) to the Constitution, 2/3 of the state legislatures. As there are 50 states, 33 would be needed for the convention to be called.
To call a convention for proposing an amendment, 34 states are required. Since 32 states have already petitioned Congress, an additional 2 states are needed to reach the necessary threshold for that step to be taken.
Forty-nine states have applied for an Article V Convention (what is often called a "Constitutional Convention"), submitting more 700 applications. Article V does not permit the calling of a "constitutional convention" only a "convention for proposing amendments."
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.
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twelve
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12 by AJ
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9 states 9 states
A total of 12 states participated in the Constitutional Convention held in Philadelphia in 1787, sending delegates at various times. Only Rhode Island did not send delegates to the convention. The convention ultimately resulted in the drafting of the United States Constitution, which was later ratified by the states.
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9 states were needed to ratify the Constitution