it looks like many dont really know how each stat is calculated and how they exactly work, so I am trying to help you with that. Of course, the information I will be proving is the same on every other wiki page regarding pokemon if you would use google, but anyway, lets begin :)

1. Basic Stats

2. IVs (Individual Value)

3. EVs (Effort Value)

4. Nature

5. All together

1. Basic Stats

First and most important the basic value each pokemon has. You can not change it, even if you catch the same pokemon multiple times. It is pretty simple to figure them out, just open the PokeDex and mouseover the green triangle. We have Health Points (HP), Attack (Atk), Defense (Def), Speed (Spd), Special Attack (SpAtk) and last but not least Special Defense (SpDef). Each stat is pretty much self explanatory, so I wont cover that and the formula which goes with them. If you really want me to do, say so and I will add to it in the future, but for now we will stay with the basics.

2. Individual Value

Now to the part, where everyone wants their pokemon to be rated by the all chat. The Individual Value, or short IVs, range from 1 to 31 and are random generated upon engaging a pokemon in the wild. You can not alter them directly, only by catching the same pokemon over and over again. There are 6^31 different possible variations, so quite a lot. It is pretty hard to get a perfect pokemon, meaning all 6 stats have to have 31 IVs in HP, Atk, Def, Spd, SpAtk and SpDef - A friendly advice, dont try to get one :)

3. Effort Value

Everyone always complains about farming EVs (short for Effort Value) you you will soon know why. Compared to IVs, you have full control over the EVs. Each pokemon you defeat can and will grant you EVs, which one depends on the pokemon you have defeated. For example, if you want your pokemon to get EVs in SpAtk, you have to defeat pokemon who will yield SpAtk and that is, for example, a Psyduck. In most cases Pokemon will yield its highest Basic Stat as EV, so you can see it directly in the PokeDex, but doesnt always has to be true. To be sure I would recommend to always check on the internet.

Now to the tricky part. You can only get a total of 510 EVs, you can distribute them how you like, but you have to keep in mind, one stat can only recieve 252 EVs. To make it more clear, lets take our Psyduck again as an example. For some odd reason you want to train your Psyduck in Atk and Def, thats fine, but it also means you have to defeat 252 Paras for Atk and 252 Geodudes for Def. If you are keeping up, you will notice we are missing now 6 EVs. You can now put 4 EVs in the third most useful spot, so we will take Spd for that, meaning you have to kill another 4 Digletts, the other 2 are leftovers and are useless and I will tell you why.

Every 4th EV will grant you 1 additional Basic Stat, that means the 252 Atk we just trained are divided by 4. Adding to our example of the Psyduck (which has a Basic Attack Value of 52) it would give us 52 + 252/4 (52 + 63). Now you may see why the 2 EV leftovers wont bother us anymore, because 2 EVs are not enough to make another 1 Basic Stat.

To summerize it:

You can train 510 total EV, but only 252 in each stat (HP, Atk, Def, Spd, SpAtk, SpDef) and if you decide to push 2 stats to the limit you will have 6 leftovers and only 4 of them will matter, the other 2 wont.

We will come back to the formula later again.

4. Nature

There are 25 different natures out there and it is totally random (like the IVs) which one you will get, but you can alter that with a Pokemon which has the ability "Synchronize". It does have a 50% chance to apply the same nature it has, to the pokemon you are engaging in the wild. There are 20 Natures which will increase and decrease one stat and 5 Natures who are "blank", meaning they dont do anything. If you select a pokemon which has one of the 20 natures you will see that one Basic Stat is highlighted in green and one in orange/red. The green is the boosted stat and the yellow/orange stat will get decreased. But different from IVs and EVs, a Nature will never touch the HP stat. A green stat is increased by 1.1, meaning 10% and a yellow/red stat is increased by 0.9, meaning it only has 90% of its total power.

5. All together

Now let's see what it can do all together, this is where the magic happens. I will take the example from earlier again, our Psyduck. Let's pretend we got ourself a fine, perfect Psyduck with 31 IVs in every Stat and trained its EVs in Atk and Def for the full amount. The basic stats are 50 HP, 52 Atk, 48 Def, 65 SpAtk, 50 SpDef and 55 Spd. Perfect that is all the information we need to calculate the stats it will have at every level. Lets take a look at the formula:

(((Basic Stat * 2 + IV + EV / 4) * X / 100 ) + 5 ) * Nature

Now we only have to insert our stats, its pretty simple, lets try it out.

Our Basic Stat for Atk is 52, we have 31 IVs in Atk and trained it all the way to 252 EVs in Atk. The X marks the level it should have, so we make it a 100 and we want it to have the Nature Adamant (+Atk, -SpAtk). Let's see what the formula looks like if we fill it in:

(((52 * 2 + 31 + 252 / 4) * 100 / 100 ) + 5 ) * 1.1 = 223.3 Atk

As we can see, our Psyduck will have 223 Atk at level 100, easy, isnt it ? :) Now we do it for the SpAtk.

(((65 * 2 + 31 + 0 / 4) * 100 / 100 ) + 5 ) * 0.9 = 149,4 SpAtk

You can do it now with every stat and you can see for yourself what your pokemon will looks like at the selected level, in this case 100. But there is one exception, that is the HP stat. It does work a little different.

(((Basic Stat * 2 + IV + EV / 4) * X / 100 ) + 10 + X

Let see how much HP our little Psyduck can get at level 100

(((50 * 2 + 31 + 0 / 4) * 100 / 100 ) + 10 + 100 = 241 HP

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And that's it. Now you can play pokemon with your calculator :) I really hope that did help you and that it will reduces the "<pokemon> rate?"-spam a little. Feel free to ask any question you might have, I would be glad to answer them.

Best regards, Bassad.