How many states had to ratify the new plan of government in order for the constitution to?

For the U.S. Constitution to become effective, it required ratification by nine out of the thirteen states. This requirement was established in Article VII of the Constitution. Once nine states ratified the document, it would officially take effect for those states, even if others had not yet ratified. Ultimately, the Constitution was ratified in 1788 and went into effect in 1789.