Combat Power

Combat Power or CP is a measurement of the strength of a Pokémon. Higher CP values mean the Pokémon has a higher Stats on Attack, Defense and Stamina combined.

Combat Power is calculated using Base Stats of Pokémon and its Individual Values, both of these statistics are hidden in the Pokémon GO.

Details
When capturing Pokémon, CP is either directly displayed, or three questions marks may show (???) if its CP is higher than any of already captured Pokémon in Trainer's collection. CP and the difficulty of catching a Pokémon is usually correlated, although this also depends on the species in question.

The higher the level a Trainer is, the higher the CP of a Pokémon can be. Trainer can Power Up their Pokémon to their Trainer level + 2. Wild Pokémon caught will also have higher CP as the Trainer levels up. Once the Trainer has reached level 30, the CP ceiling for wild Pokémon is capped at level 35. A similar cap for Pokémon hatched from eggs is reached at 20.

The arc above a Pokémon on its page indicates how high its CP is relative to its CP potential with a dot. A Pokémon at level 1 (10 CP) would be all the way to the left, a Pokémon at the maximum level at Trainer Level would be all the way to the right. This is not to scale however, as from a perspective of a level 30 player, a level 10 Pokémon would have the dot roughly in the middle.

Individual Values
Individual Values or IVs can determine if a Pokémon is stronger in battle than another Pokémon of the same species, as they are unique to each Pokémon obtained.

They have a range from 0 to 15. The 3 Individual Values are Attack, Defense, and Stamina. Pokémon Appraisal allows Trainer to check them. Each Pokémon species has base stats. The base stats are the lowest possible IV for that species. If a Pokémon's stats matches the base value, they are considered to have an IV of zero.

There are external tools, such as Pokémon IV Calculator to help Trainer determine its chance of having "perfect" IVs.

Values types
Helps determine how much damage the Pokémon does in battle, and also has the highest influence on CP.
 * Attack

Helps determine how much damage the Pokémon can receive in battle, and also has an influence on CP.
 * Defense

Helps determine HP and CP levels of the Pokémon.
 * Stamina

Relationship with obtain methods
Pokémon obtained from different methods have IV floors, which mean all three values are not lower than a certain number. This is likely to make those obtain methods more rewarding.

Some methods include a set CP level of Pokémon given. Therefore, certain IV (especially maximum and minimum) can be interpreted by simply checking the CP value.

Pokémon from GO Snapshot is treated as wild Pokémon, but they cannot be weather boosted.

Hit Points formula
$$HP = (Base Stam + Stam IV) ~ \times ~ Lvl(CPScalar)$$

Combat Power formula
$${CP = \frac{(Base Atk + Atk IV) ~ \times ~ \sqrt{Base Def + Def IV} ~ \times ~ \sqrt{Base Stam + Stam IV} ~ \times ~ Lvl(CPScalar)^{2}}{10}}$$

Where  is: