Hidden power is a very random move between each pokemon, and has a lot of potential in a pokemon battle. You may have already taught it to a pokemon and discovered that this seemingly normal-type move can land super effective hits on certain types, which isn't a trait of the normal type. You may see a low effect of power from the move in battle, or a heavy hit from it. What determines what this move does? What is this move anyway?

Well first, let's explain what you can get from this move. If you look at the move description in the game, it doesn't give a definite power, marks it as a normal type move, and says, "The attack power varies among pokemon." There's only one false statement within that move description, and that's the fact that it is a normal type move. In reality, this move can be any type BUT a normal type move. Personally, I think this move should be right along with Curse with the ???-type description. The attack power is going to be a number between 30 and 70, which causes the randomness in base power between pokemon.

"70? That's kinda low, don't you say?" If you compare it to other moves like Overheat with 140 base power, then yeah, it is kind of low since Hidden Power has only the potential to amount to half of the power Overheat has. But once again, it still has a lot of potential to help. Say you have a Registeel, a steel type pokemon. The best steel type move it can learn is Steel Claw, and that doesn't amount to much unless you use Curse a few times, and still Pokemon can overcome it. However, if you are able to get the right Individual Values, Hidden Power suddenly becomes a better choice for a move if you can get it to be Steel type, and have 70 base power at the same time. (Individual Values are going to be explained within the weekend.) Another scenario could be for Ninetales, a fire pokemon. It has a good potential to be a Special Sweeper, but it can only learn a single type of move that's associated with the Special Attack stat, which is Fire type. If you give it a Hidden Power that can make use of Special Attack, it can get even deadlier for many different types.

So how do you go about finding the power and attack type of this move? Well let's start with the easier part – the type. You can find the type out by battling different types of pokemon and going through a process of elimination, like if the Ninetales mentioned before used hidden power on Nosepass and it was super effective, then you could assume that it's either ground, rock, water, or grass type and go from there. Or you could do it the other way through algebra, which needs a basic knowledge of mathematics to figure out, and an IV value for all six stats. The equation to find the base power is this:

HP Type = (T1 + T2 + T3 +T4 + T5 + T6) * 15 / 63

Please note that the * means "multiply by" and the / means to "divide by". Anyway, you're probably wondering what the T1's all mean, so I should explain those now. Those are variables, or things that can mean an infinite number of values unless defined. We can't make use of the equation unless we define them, so let's make use of the IV values now. The values basically go like this:

If IV of Hit Points is odd, then T1 = 1.
If IV of Attack is odd, then T2 = 2.
If IV of Defense is odd, then T3 = 4.
If IV of Speed is odd, then T4 = 8.
If IV of Special Attack is odd, then T5 = 16.
If IV of Special Defense is odd, then T6 = 32.

If by chance you happen to get a number that is not odd or divisible by two, then that particular variable will be equal to zero. Now say the Ninetales from before had these IVs:

HP = 31
Attack = 31
Defense = 30
Speed = 31
Sp. Attack = 30
Sp. Defense = 31

Yeah, I know that they're kinda high, but this is just for example purposes. After we use these IV's to make some sense with our current information, we come up with this:

HP Type = (1 + 2 + 0 + 8 + 0 + 32) * 15 / 63
HP Type = (43) * 15 / 63
HP Type = 645 / 63
HP Type = ~10

If you don't know, the ~ sign in algebra means "about". It's what gets put in front of a value with un-needed decimals, and we can't use a number with decimals for the equation. If you want to know the decimal that we got, it was about 10.2. If it was 10.5 or above, the value would turn out to be ~11 instead. Anyway, we got 10 for the HP type, but that isn't a type. We have to input the number into a table to get the type.

Here's the table:
If HP Type = 0, then the type is Fighting.
If HP Type = 1, then the type is Flying.
If HP Type = 2, then the type is Poison.
If HP Type = 3, then the type is Ground.
If HP Type = 4, then the type is Rock.
If HP Type = 5, then the type is Bug.
If HP Type = 6, then the type is Ghost.
If HP Type = 7, then the type is Steel.
If HP Type = 8, then the type is Fire.
If HP Type = 9, then the type is Water.
If HP Type = 10, then the type is Grass.
If HP Type = 11, then the type is Electric
If HP Type = 12, then the type is Psychic.
If HP Type = 13, then the type is Ice.
If HP Type = 14, then the type is Dragon.
If HP Type = 15, then the type is Dark.

So now we can see why it was super effective against the Nosepass now, because it was the Grass type. But now we need to calculate one more thing that is equally important – power. That's obtained generally the same way as the type is, with a different equation of course. Here it is:

HP Power = (P1 + P2 + P3 + P4 + P5 + P6) * 40 / 63 + 30

So yeah, now we have a bunch of variables again. Here are the values:

If IV of Hit Points divided by 4 has a remainder of 2 or 3, then P1 = 1.
If IV of Attack divided by 4 has a remainder of 2 or 3, then P2 = 2.
If IV of Defense divided by 4 has the remainder of 2 or 3, then P3 = 4.
If IV of Speed divided by 4 has the remainder of 2 or 3, then P4 = 8.
If IV of Special Attack divided by 4 has the remainder of 2 or 3, then P5 = 16.
If IV of Special Defense divided by 4 has the remainder of 2 or 3, then P6 = 32.

Understand that? Probably not. Luckily, there's only 31 different values that can appear for IV's so we can limit the possibilities down to a few values. These values are the ones that will always work: 2, 3, 6, 7, 10, 11, 14, 15, 18, 19, 22, 23, 26, 27, 30, and 31. So since both of the two values we use match to some of the values that will work, we can solve the equation now:

HP Power = (1 + 2 + 4 + 8 + 16 + 32) * 40 / 63 + 30
HP Power = (63) * 40 / 63 + 30
HP Power = 40 + 30
HP Power = 70

If you're wondering how I went from step 2 to step 3 like that, it's because I saw that both sides of the division sign had 63 on them, so I realized that it would make it easier for me to do if I just removed the two values altogether since I would end up with the same answer anyway.

And guess what? There's no fancy table we have to look through for the Base Power of Hidden Power because we've already gotten a value from the equation – 70. So this Ninetales with HP Grass is actually a very good pokemon, no doubt about that since it covers four of its weaknesses.

That basically covers anything on Hidden Power.

Btw, I'd like to thank 'Fro Dizzy on the forums for giving me the info I needed most, which was the power calculation stuff. :P Without that this guide might not exist.
Thanks to Dragonair for writing this for us