Now that the new gym system has been released in Pokemon Go, the way that Pokemon are defeated in battle has been completely tweaked. The game now relies on a system of motivation, with this motivation bar being tied to the Pokemon’s CP, which you can drain in battle. So how quickly do Pokemon lose CP in gym battles? How many battles will it take to defeat one?
It appears that at this time, the way the system works is that a Pokemon loses 28 percent of its max CP after being defeated in a battle, at least for the first two battles. Then, the third battle is generally enough to reduce the Pokemon’s CP down to zero, and so you should be able to take down a Pokemon in a gym in just three battles.
This is how the formula is as of Sunday, June 25th, and it’s possible that Niantic will tweak this again in coming days. After all, when the new gym system launched just a few days ago, Pokemon lost only about 15 percent CP in battle, and it took about five battles to drain CP to zero. A lot of players complained that this was much too difficult, and so Niantic seems to have taken their complaints into consideration by allowing players to defeat Pokemon in three battles, not five.
The CP change was observed on Reddit by user RyanoftheDay, who pointed to an example of a battle with Blissey. Blissey’s starting CP was 2726, and after the first battle, it lost 761 CP, i.e. 28 percent of 2726. In the second battle, Blissey again lost 761 CP, the exact same amount as before. Then, on the third battle, Blissey’s CP was drained to zero.
A Pokemon is kicked out of a gym when its motivation reaches zero, and it appears that a Pokemon’s motivation reaches zero after its CP is down to 20 percent. At this point, the Pokemon just needs to be defeated in battle one more time and it will be kicked out of the gym.