It can take as much as twelve weeks for a tadpole to become a frog. This however differs from species to species and on environmental conditions as well. For instance the absence of predators generally results in the tadpole stage being extended. Colds weather also results in a delay in metamorphosis. In certain cases tadpoles can delay a complete change over even after they have developed fore legs. Since tadpoles require a lot of water species that inhabit drier climates change over quickly to frogs while those in wet climates remain for a longer duration in the tadpole stage. The tadpole of the Variegated River Tree Frog remains a tadpole for around two months the eastern banjo frog on the other hand remains a tadpole for around twelve to fifteen months.
It depends what species it is
Depends on the water tempo, the amount of critters in the space, the size of the space, the kind and amount of food, and the kind and size of the tadpole. Genarally, the bigger the tadpole, the longer it takes to become a frog.