Combat Stages

Many Moves alter Stats by raising or lowering “Combat Stages”, making them more formidable or less threatening respectively. Only Attack, Defense, Special Attack, Special Defense, and Speed may have Combat Stages. HP and Hit Points never have Combat Stages.
Moves and effects may change Combat Stages any number of times, but they may never be raised higher than +6 or lower than -6. For every Combat Stage above 0, a Stat is raised by 20%, rounded down. For every Combat Stage below 0, a Stat is lowered by 10%, rounded down.
This means that if a Stat has raised 6 Combat Stages; its affected stat should be 220% of its original value. If a stat has been lowered 6 Combat Stages, its affected stat should be 40% of its original value. Consult the chart on the right to see the multiplier for any given Combat Stage. To derive the correct value for a given Stat, simply multiply the Stat by the multiplier next to the corresponding combat stage.
One easy way to apply Combat Stages for Defense, Special Defense, and Speed is to simply remember that Stat Evasion is also equal to 20% of a Stat. This means each positive Combat Stage is equal to the Evasion you gain from that Stat, at least until you reach the point where you would have more Evasion than the cap.
Combat Stages remain until the Pokémon or Trainer is switched out, or until the end of the encounter.
Speed Combat Stages and Movement
Combat Stages in the Speed Stat are special; they affect the movement capabilities of the Trainer or Pokémon. Quite simply, you gain a bonus or penalty to all Movement Speeds equal to half your current Speed Combat Stage value rounded down; if you are at Speed CS +6, you gain +3 to all Movement Speeds, for example. Being at a negative Combat Stage reduces your movement equally, but may never reduce it below 2.

Combat Stage	Multiplier
-6	x 0.4
-5	x 0.5
-4	x 0.6
-3	x 0.7
-2	x 0.8
-1	x 0.9
0	x 1
1	x 1.2
2	x 1.4
3	x 1.6
4	x 1.8
5	x 2
6	x 2.2