Effort Value Points (or EVs) are unseen statistics that can increase your Pokémon's stats. The system was introduced in the third generation (Ruby, Sapphire and Emerald). EVs are obtained by fighting other Pokémon. Depending on the defeated Pokémon, different EVs will be obtained. For example, Sneasel will provide speed EVs, while Chansey will give HP EVs. For every four EVs obtained in one stat, that stat will be increased by one extra point at level 100. Simply put, if your Gyarados were to obtain four Attack EVs, at its next level up its Attack stat would get +4 instead of +3, if it gets eight EVs it will be +5 and so on. While this is very useful, there is a catch. After accumulating 510 EVs, the game will stop tallying them and EV training becomes useless for that Pokémon. So that means that after you gain all of your EVs, the total increase in stats for you Pokémon will be +127. There is also a cap on the amount of EVs you can gain in one stat. After your Pokémon has gained 255 EVs on a stat (such as Attack), the game will stop tallying EVs for that stat. This means that the said stat will cap off with +63. This doesn't mean that it has to stop gaining EVs, it just means that once it hits that mark, it'll have to get EVs in another stat, such as Defense or Special Attack.
Methods of Making the Process Easier
EV training can become a very tedious process. Fortunately, there are items and effects that can make this whole process go by much more quickly.
- Macho Brace. This doubles the amount of EVs gained in a battle. For example, if you killed a Machoke, instead of getting 2 atk Evs, you would get 4 atk EVs.
- "Power" Items (Generation IV and later). These items will only work for one stat and will reduce the pokémon's speed while held. They increase the described stat by four. These are Power Weight (HP), Power Bracer (ATK), Power Belt (DEF), Power Lens (SPATK), Power Band (SPDEF) and Power Anklet (SPD). If your pokémon was holding a Power Bracer (ATK) and it killed a Machoke, instead of 2 ATK EVs, you would get 2 + 4 = 6 ATK EVs; If your pokémon was holding a Power Belt and it killed a Machoke, besides getting the 2 EVs on attack, you would also get 4 EVs on Defense.
- PokeRus. This is a super rare beneficial virus (made less and less rare in newer versions) that can be obtained in battles against wild Pokémon. It has the same effect as the Macho Brace, but will wear off if the infected Pokémon is in your party when the DS internal clock reached midnight. However, the virus can be kept indefinitely if the Pokémon is kept in the Box. Can be passed along party Pokémon by battling; it will pass to any pokémon situated next to the infected Pokémon after a battle. NOTE: It might not pass after any battle, as it may pass, it is random. How it works: Imagine your pokémon is holding a Power Bracer and defeats a wild Machoke; it would get (2 + 4)*2 = 12 ATK EVs. Another example: Your pokémon is holding a Power Belt and it defeats a Wild Machoke; you will get 2*2 = 4 ATK Evs and 4 DEF EVs.
- HP UP, Protein, Iron, Calcium, Zinc and Carbos. These add 10 EVs to their respective stat until a cap of 100 EVs. Very practical as they cost 1 BP.