A Beginner's Guide to Understanding EVs

Introduction

Effort Values, or EVs as they're commonly known, are an integral part of competitive Pokémon battling. If you are a newcomer, you may have seen this term thrown around on analyses, or you may have played around with the EV sliders on Pokémon Showdown!'s teambuilder. Either way, understanding what they do and how they're used is a huge part of becoming a better player.

Essentially, EVs are points that can be added to any of a Pokémon's six stats to increase them. They can be added in any combination the player desires, giving the player the freedom to modify their Pokémon's stats in unique ways. Because of this, EVs can drastically change the role a Pokémon plays in battle and its matchup against other Pokémon. EVs can only add to a stat, not subtract, so a Pokémon with EVs is ALWAYS superior to a Pokémon without them. With that said, EVs don't have as much of an effect when they're not distributed across stats effectively, so all Smogon analyses include a recommended EV distribution, known as an "EV spread." Understanding how these most efficient spreads are determined and why they are effective is very important for teambuilding, battling, and maximizing your own innovative capabilities.

As a side note: EVs are NOT the same thing as IVs. While they both contribute to the final stats of a Pokémon, IVs are much simpler and should generally always be 31.

Basic Mechanics

Every Pokémon can have a maximum of 510 EVs in total and a maximum of 252 EVs per stat. At level 100, EVs are worked with in multiples of 4, as a Pokémon gains a 1 point stat increase for every 4 EVs that are added. At level 50, EVs are worked with in multiples of 8, as a Pokémon gains a 1 point stat increase for every 8 EVs that are added. One important side note is that at level 50, a stat with 31 IVs will start increasing at 4 EVs and then increase with every 8 EVs (4, 12, 20, 28, and so on) whereas a stat with 30 IVs will always increase with every 8 EVs (8, 16, 24, 32, and so on).

At level 100, the difference between a stat without any EVs and one that's fully invested is 63 points, which is a major difference. Take Sand Rush Excadrill, for example, a common sand sweeper in OU:

0+ Atk Life Orb Excadrill Earthquake vs. 0 HP / 0 Def Keldeo: 218-257 (67.4 - 79.5%) -- guaranteed 2HKO

Without any Attack investment, Excadrill will be taking away a little over two-thirds of Keldeo's health with Earthquake. This is certainly respectable, but it's insufficient because Keldeo can KO back with any of its moves.

252+ Atk Life Orb Excadrill Earthquake vs. 0 HP / 0 Def Keldeo: 263-309 (81.4 - 95.6%) -- guaranteed 2HKO

Once invested with Attack EVs, Excadrill can OHKO Keldeo with three switches into Stealth Rock or three turns of sandstorm damage, which should be very easy considering this Excadrill set is used on sand teams.

Because EVs are added to a stat before the effects of multiplicative items such as Eviolite, Choice items, and Life Orb, investing EVs into a stat will have an even greater effect when you use these kinds of items.

General Trends

In most cases, EVs are used to buff up stats that are already good rather than patch up stats that are poor. In fact, many, if not most, Pokémon sets use a simple 252 / 252 / 4 spread, with the two stats with 252 EVs corresponding to its most important ones (the 4 remaining EVs are leftover and can usually be put anywhere). When choosing which stats are most important to invest EVs in, the following guidelines are generally followed:

For most offensive Pokémon and many defensive and support Pokémon, Speed is the most important stat to invest in. This is because outspeeding other Pokémon plays a critical role in battle.
When opting for overall bulk, such as on a bulky attacking Pokémon, HP is invested in instead of individual defensive stats. Conversely, individual defensive stats are generally invested in only when the Pokémon is explicitly meant to play a defensive role.
With very few exceptions, Attack and Special Attack are rarely invested in at the same time. This is because the vast majority of offensive Pokémon do not have the capability to go mixed, and even those that do often have a "primary" offensive stat that is used more often and therefore worth the investment.
As explained in the last section, boosting items such as Choice items will cause EVs to have a greater effect, so this is also taken into consideration when determining which EVs to invest in. For example, Assault Vest Conkeldurr invests into Special Defense instead of HP because the Special Defense investment makes the 1.5x boost from Assault Vest more effective.

By keeping these guidelines in mind, you should have greater success when making your own EV spreads when teambuilding. Of course, all Smogon analyses have recommended EV spreads along with an explanation, but it's an extremely valuable skill to be able to determine the most effective EV spreads for your Pokémon regardless of whether or not it's an established set.

Benchmarks

The more specialized a Pokémon's role is, the more specialized its EV spread will likely need to be. For example, offensive Dragon Dance Altaria simply needs to be fast and do a lot of damage, so it uses a basic 252 Atk / 252 Spe spread. However, defensive Dragon Dance Altaria is meant to be able to take specific hits to boost up against a wider variety of threats, so it uses a much more complex spread of 248 HP / 136 Def / 96 SpD / 28 Spe. This spread has been specifically tailored to match its more intricate role.

The irregularity of the above spread, and of most other complex spreads, is the result of the Pokémon attempting to reach certain benchmark stats. In general terms, a benchmark is an important stat value that guarantees a specific result in a specific situation. For example, Mega Lopunny and Mega Manectric are some of the fastest Pokémon in OU, and they both have base 135 Speed, which becomes a Speed stat of 405 when fully invested. So for any OU Pokémon attempting to boost their Speed and sweep, going above the benchmark of 405 Speed means they can no longer be revenge killed by Mega Lopunny and Mega Manectric. The 28 Speed EVs in Altaria's defensive Dragon Dance set give it exactly 406 Speed after two Dragon Dance boosts, allowing it to surpass this common benchmark.

Benchmarks exist in other stats, too. For example, a Pokémon weak to Stealth Rock that switches in and out a lot may adjust its HP stat to ensure it will survive four switches in (do be aware, however, that careless HP investment can also make a Pokémon slightly MORE vulnerable to Stealth Rock as well). A mixed attacker with a surprise coverage move may increase its non-dominant attacking stat just enough to guarantee a 2HKO on one of its common checks. Additionally, in the Altaria example above, the complex defensive investment guarantees it will never be 2HKOed by Pokémon like Life Orb Thundurus, so the player knows that Altaria can always boost up against an opposing Thundurus and simply Roost off the damage.

For determining Speed benchmarks, your most helpful resource will be the Speed Tiers lists located in every tier's subforum (and linked at the bottom of the article). These lists contain every common Pokémon in the tier and what Speed they reach, taking into account boosting moves, natures, EVs, and even items like Choice Scarf. They're listed in descending order from highest to lowest, so they give you a very easy way to see what your Pokémon will and will not be outspeeding with any Speed stat.

For other stats, the Pokémon Showdown! damage calculator (also linked at the bottom of the article) is a great resource that lets you see how much damage two Pokémon will do to each other and puts you in control of variables like EVs, natures, items, weather, and anything else that could possibly affect the damage done by a Pokémon. It also lets you add in factors like entry hazards, so you can even adjust your EVs to OHKO a certain Pokémon after it switches in on Spikes, for instance.

In Battle

In Pokémon battles, both on the cartridge and Pokémon Showdown!, you're not told what your opponent's Pokémon's stats or EVs are. While it may be hard to find out their exact values, you can actually make very educated guesses based on context clues. If you can pay attention to subtle clues like how much damage the opposing Pokémon's attacks do, how much damage it takes itself, and what it is or isn't capable of outspeeding, you can use this information to make smarter plays.

For example, let's say your opponent switches in their Excadrill to tank a Draco Meteor from your Life Orb Latias, and it loses about 30% of its health. This is extremely important—a quick check on the Pokémon Showdown! damage calculator tells you that only Excadrill's bulky spinner set could possibly take 30%, as it has full HP and Special Defense EV investment. By contrast, the vast majority of offensive Excadrill won't invest in HP or Special Defense, instead opting for Speed and Attack. This information is incredibly valuable—perhaps later in the battle, your offensive Heatran is up against this Excadrill. Normally, it would be incredibly risky to stay in, as the common offensive Excadrill can easily outspeed Heatran and OHKO it with Earthquake. But now, because you know the Excadrill doesn't have any Speed EVs, you can be confident your Heatran with full Speed EVs can outspeed it and hit it with a super effective STAB Fire Blast.

That's just one example of how having knowledge of EVs is incredibly valuable. Correctly guessing your opponent's EV spreads also allows you to look on the Smogon Strategy Pokédex and find out what moves the foe might be running, what specific benchmarks the set is trying to hit, and other useful information.

Conclusion

Overall, having a strong understanding of EVs is critical to improving your skills as a Pokémon battler and teambuilder. Good EV spreads can mean the difference between a mediocre Pokémon and a terrific one, and being able to discern your opponents' EV spreads while being cognizant of your own gives you a supreme edge in battle. While it may seem like an impossible task to keep track of so many numbers, awareness of EVs comes naturally and will become a seamless part of your planning and playing. Remember to use the resources below to help you!