From Bulbapedia, the community-driven Pokémon encyclopedia.
- If you were looking for the in-battle stat, see Stats → Accuracy.
Accuracy is an aspect of moves that determine how often they can hit their target.
A move's base accuracy currently can be any number from 1-100, reflecting the probability of the move hitting as a percentage; moves' accuracy was not visible to the player until the Generation III games. While values from 1-100 for accuracy are possible, only values from 30-100 are used, and they are only used in multiples of 5.
Many moves have an accuracy of "—%", indicating that they are exempt from accuracy calculations. This is usually because they affect no one but the user (and/or the partner in a Double Battle), or because they will never miss the target unless the target uses a move that grants semi-invulnerability for a turn (such as Fly or Dig).
Accuracy can be increased by Abilities, held items, and increasing the accuracy stat; Compound Eyes raises the Pokémon's accuracy by 30%, Victory Star raises a Pokémon's accuracy by 10%, the Wide Lens raises the holder's accuracy by 10%, and the Zoom Lens raises the holder's accuracy by 20% if the holder moves after its target. The accuracy stat can be increased by Acupressure, Hone Claws, Coil, Moody, and X Accuracy*.
Accuracy can be decreased by Abilities, held items, and moves. Hustle decreases the accuracy of the Pokémon's physical moves by 20%. The accuracy stat can be decreased by Flash, Kinesis, Mirror Shot, Mud Bomb, Mud-Slap, Muddy Water, Octazooka, Sand Attack, Smokescreen, and Secret Power when used in the sand, on plain terrainDPPtHGSS, in puddlesDPPtHGSS, and on rocksXYORAS.
Formula for accuracy and evasion
The probability that a move will hit is calculated as follows:
- Abase is the base accuracy of the move (in percent - e.g. a base accuracy of 95 is counted as 0.95),
- Accuracy is the current accuracy stat of the user (in percent - e.g. raising accuracy by three stages raises this number to 2), and
- Evasion is the current evasion stat of the target (in percent - e.g. lowering evasion by two stages lowers this number to 0.6).
If P is greater than 1, the move will surely hit. In a Double or Triple Battle, it is possible for a move that targets multiple Pokémon to hit some and miss others—the probabilities are calculated individually for each Pokémon.
1/256 miss glitch
In the Generation I handheld games, even moves with 100% accuracy would miss once in a great while for seemingly no reason whatsoever. This was due to accuracy being internally stored as a single byte ranging from 0 to 255 (0 to FF in hexadecimal), and the probability of a move hitting being determined by generating a random byte and ensuring that it was less than the accuracy value. There was therefore a 1/256 chance of the random byte being equal to 255, which could never be less than even the highest possible accuracy value, causing moves labeled as being 100% accurate to miss 1/256 of the time and yielding an effective accuracy of about 99.6%. (It was not possible to replace the "less than" check with a "less than or equal to" check, as this would enable moves with 0 accuracy to hit 1/256 of the time when the random byte was equal to 0.) This bug also applied to secondary effects such as poison or paralysis, as well as critical hits. Swift was unaffected, as its effect automatically skips all accuracy checks (including, incidentally, the invulnerability effects of Fly and Dig) and thus truly has 100% accuracy.
The bug was partially fixed in Pokémon Stadium by allowing the move to hit if the random byte was either less than the accuracy value or exactly equal to 255; this fix effectively causes every move in the game to hit 1/256 more often. The fix did not apply to critical hits, which were still capped at a 255/256 probability. It was further fixed in Generation II, which removed this extra check and instead allowed moves calculated to have 100% accuracy (after applying all modifiers) to skip the random byte generation entirely. However, this did not apply to Protect, which still has a 1/256 chance to fail when used for the first time. All 1/256-related bugs were finally resolved in Generation III, whose hardware gained the ability to more freely generate ranges of random numbers; move accuracies are stored as a number from 0 to 100, and the game performs a "less than or equal to" check on a random integer from 1 to 100.
In the Pokémon Mystery Dungeon series
In the Pokémon Mystery Dungeon series, accuracy is instead called "Hit Ratio" and is displayed with a number of stars instead of a numerical value. More stars indicates a higher accuracy. For example, Scratch has a Hit Ratio of .
Hit Ratio does not correlate with accuracy from the main series. Some moves, such as Scratch and Crunch, share the same accuracy in the main series but have different Hit Ratios (or vice versa).