What level will Eevee evolve?

None of its evolutions requires a specific level. Here are the steps on how to evolve Eevee into which evolution you want. Using a Water Stone on it will evolve it into Vaporeon, a Thunder Stone will evolve it into Jolteon and a Fire Stone will evolve it into Flareon. If you're training your Eevee in the day time and it levels up and it's happy enough, it'll evolve it'll Espeon. If you're training it at night and it levels up and it's happy enough, it'll evolve into Umbreon. Evolving into Leafeon and Glaceon depend on where you're training at in the Sinnoh games, if your Eevee levels up in the grass patch near the Moss Rock in Eterna Forest then it'll evolve into Leafeon but if it levels up in the grass patch near the Ice Rock which is close to Snowpoint City then it'll evolve into Glaceon.