How does damage calculate?

I'm not someone who can just function off "the bigger number is better" I need to understand why x amount of damage happens instead of x amount. For example why does a move that has 100 power that is doing neutral damage only doing 20 hp in damage. I'm well aware it has to do with the opponents defensive value and your own attack value but exactly how does it function?

For all the formulae and mathematics that go into calculating damage (just like many other things in the Pokemon games), there's still the element of randomness to it as well. For example, even if all the other conditions remain the same, one attack could do 51 HP of damage the first turn, and then 48 HP the second. Bulbapedia probably has the best explanation of how damage is dealt here, though there's quite a bit to read through.

Anyway, since this topic is geared towards game mechanics rather than the franchise as a whole, I'm going to move this over to Pokemon Gaming Central for you.

MOVED.

i wonder how they worked out with a complex equation for damage like that. there's a lot of pretty arbitrary numbers and coefficients in it. did they come up with that just kinda randomly or was it based on something else? /nerd