Level 20.
Gyarados doesn't evolve as it is the max evolve form of magikarp. Magikarp evolves into Gyarados at level 20.
Magikarp evolves into Gyarados at Level 20.
Magikarp evolves into Gyarados at level 20.
Magikarp evolves into Gyarados at level 20
Magikarp evolves into Gyarados at level 20.
Magikarp evolves at LEVEL 20 to Gyarados.
Magikarp can evolve into Gyarados, starting at level 20.
Magikarp evolves into Gyarados at level 20
Magikarp evolves into Gyarados at level 20.
Gyarados do not evolve. Magikarp evolve into Gyarados at lvl. 20
Magikarp evolve into Gyarados at level 20
Magikarp evolves on level 20 into a gyarados.