To start out, a critical hit occurs when the critical hit value exceeds a number that is randomly generated for each hit. Naturally, the higher the value, the better the chance that it will be higher than that randomly generated number. As with many other variables in the game, the scale for critical hit value and the randomly generated number goes from 0 to 255.
In R/S all pokemon have a base critical hit value of 17, which gives a 6.6% chance of getting a critical hit. This value can be modified by the moves and/or items used by a pokemon. These increases will change the value to different levels on a fixed scale for critical hits. The scale is as follows:
| Critical Hit level | Critical Hit value | Critical Hit % chance |
|---|---|---|
| 0 (base) | 17 | 6.6% |
| 1 | 32 | 12.5% |
| 2 | 64 | 25% |
| 3 | 85 | 33.2% |
| 4 | 128 | 50% |
All pokemon start at the base level of zero, therefore the only other thing to consider is the moves and items that can increase that level and by how much they do so. Those values can be shown as follows:
| Levels increased | Move | Item |
|---|---|---|
| 1 | Focus Energy | Scope Lens |
| 2 | Aeroblast
Air Cutter Blaze Kick Crabhammer Cross Chop Karate Chop Leaf Blade Poison Tail Razor Leaf Razor Wind Slash |
Lucky Punch(only when equipped on Chansey)*
Stick(only when equipped on Farfetch'd)* |
*Note: The use of these two items are the only Critical Hit modifiers that will function on the pokemon that are properly equipped with them. This is done to remove the possibility that the Critical Hit level will exceed 4.
The information in the two tables above are all that is really needed to determine what the chances of a critical hit will be for a given attack. However, a couple of examples may clarify things further, in case the information above hasn't quite solidified in the reader's mind.
Example 1:A Blaziken using the move Blaze Kick.
From the tables above we get this analysis:
Blaze Kick, a high CH move = +2 levels
base + 2 levels = level 2 on the scale = 25% chance of a critical hit
Example 2: A Slaking with the Scope Lens item using the move Hyper Beam.
Scope Lens equipped = +1 level
base + 1 level = level 1 on the scale = 12.5% chance of a critical hit
Example 3:A Machamp, that has been Baton Passed to by a pokemon that used Focus Energy and Swords Dance once, is equipped with a Scope Lens and is using the move Cross Chop on a Skarmory.
Scope Lens equipped - +1 level
Focus Energy - +1 level
Cross Chop - +2 levels
base + 4 levels = level 4 on the scale = 50% chance of taking only one hit to turn that annoying tin turkey into scrap! *Ahem* A 50% chance of a critical hit that could make a difference.
One final note about Critical Hits on 2 on 2 battles, for the sake of being explicit. Just as hit determination is seperate for each target for attacks that strike multiple pokemon, the same is true for Critical Hit determination. In other words, if an attack hits both foes (and even the ally) getting a Critical Hit on one doesn't guarantee that you'll get a Critical Hit on the other target(s).
To put it simply, Critical Hits do twice the amount of damage of a non Critical Hit. Of course, it's not entirely that simple, or no one would put up a page about it.
First off, the simplest part of the damage calculation are held items that affect damage. These include: Choice Band, pokemon-specific boosters (such as Light Ball for Pikachu or Soul Dew for Latios), and type boosters (such as Charcoal or Miracle Seed). The effects from all of these will always be factored into the damage, even for items that boost the defensive ability of a pokemon (such as the aforementioned Soul Dew).
Next are damage-affecting moves. These include: Charge, Helping Hand, Light Screen, Mud Sport, Rain Dance, Reflect, Sunny Day, and Water Sport. Of all of these moves only Light Screen and Reflect do not have their effects retained for the damage calculation during a Critical Hit. The rest will have their effects retained, regardless of whether it would result in a greater or lesser amount of damage.
Finally, we come to the most complex set of factors involved in Critical Hit damage: stat changes. Stat changes may be retained for the calculation or dropped as necessary in order for the Critical Hit to cause as much damage as possible. The rules for how this is accomplished by the game breaks down as follows:
If there are a mix of stat changes in play when the Critical Hit occurs, they will be retained or ignored as dictated by the rules noted above. For some, how that will apply to every situation is obvious. For those people, that's all there is to know about Critical Hits. They can stop reading this page and move onto doing something else with their time. For others, how this might work in a given situation may not be clear. There are a few examples for this group:
Example 1: A pokemon has used Swords Dance once and scores a Critical Hit with no other stat changers in play. This stat change will be retained for the damage calculation of the Critical Hit.
Example 2: A pokemon has used Acid Armor once and the opposing pokemon gets a Critical Hit against it while no other stat changes are in play. This stat change will be ignored for the damage calculation of the Critical Hit.
Example 3: A pokemon has used Swords Dance once and scores a Critical Hit against a pokemon that has used Acid Armor once. The stat change provided by the use of Swords Dance will be retained, but the stat change from the use of Acid Armor will be ignored.
Example 4: A pokemon has been hit by Charm once, reducing its Attack stat by 2 levels. When this pokemon scores a Critical Hit, this reduction of its Attack stat will be ignored for the damage calculation.
Example 5: A pokemon has used Swords Dance twice and has been hit by Charm once. Assuming that those are the only stat changes in play, the net result of the stat changers puts the Attack stat above normal. When a Critical Hit occurs, all of these stat changes will be retained for the damage calculation.