Understanding RBY mechanics

By p2. Art by Bummer.
« Previous Article Home Next Article »
Understanding RBY mechanics by Bummer


RBY mechanics are well known for being drastically different compared to those of later generations, and these mechanics completely define the RBY metagame that players still enjoy to this day. Even though the games are 20 years old now, there are still mechanics that have yet to be discovered; for example, one of the most metagame-changing mechanics, the fact that secondary effects cannot affect Pokémon that share the same type as them, was only discovered last year. This completely changed the metagame and heavily impacted the viability of certain Pokémon, especially Rock-types.

In RBY, Fairy-, Steel-, and Dark-types don't exist, so moves such as Bite are Normal-type and Pokémon in the Magnemite family are pure Electric-type. There are also no hold items, abilities, or Team Preview. Whether a move is physical or special depends on its type, which means that all Normal-, Ground-, Rock-, Fighting-, Poison-, Ghost-, Bug-, and Flying-type moves are physical, while all other types are special.

RBY also uses DVs instead of IVs, and instead of a limit of 31, DVs are limited to 15, but for every 50 levels of the Pokémon, 1 DV gives your Pokémon an extra stat point. This means that at level 100, your Pokémon gains 2 stat points per DV. Natures don't exist, which means that the highest stats of Pokémon are drastically reduced compared to those in modern Pokémon games. An example of this is Starmie, which hits 328 Speed at level 100 in RBY, but in generations after GSC, hits 361 Speed. Instead of EVs, there's Stat Exp, going from 0 to 65535. When you defeat a Pokémon, you will get Stat Exp in accordance with its base stats. For example, defeating Mew grants 100 Stat Exp to each stat. More information about this in this link.

The mechanics

In this article, I will cover some of the most important mechanics and how they alone completely make RBY unique.

Critical hits

In RBY, critical hits work much differently than they do now. Critical hit rates are based on the user's base Speed stat and not a 6.25% chance. The formula for critical hit rates is Critical Hit % = Base Speed * 100 / 512. This means that Pokémon with a base Speed of 100 will have a critical hit rate of 19.5%, while the fastest Pokémon in the game, Electrode, has a whopping critical hit rate of 27.3%, and the slowest Pokémon in the game (Parasect, Slowbro, Snorlax, and Lickitung) have a measly critical hit rate of 5.86%. Critical hits are also based off the Level of the Pokémon, which is doubled for the damage calculation. On average, critical hits deal around 1.95x damage at Level 100 while they only deal 1.5x damage at Level 5. In generations after RBY, critical hits always dealt 2x damage, but as of XY, all critical hits deal 1.5x damage unless the Pokémon has the ability Sniper. High critical hit rate moves such as Slash, Razor Leaf, Crabhammer, and Karate Chop use a different formula: Critical Hit % = Base Speed * 100 / 64. This means that even Parasect has a 50% chance to land a critical hit when using Slash, despite being one of the slowest Pokémon in the game.

Critical hits also ignore your own Pokémon's boosts, meaning that even a Slowbro at +6 Special would only deal the same damage with a critical hit as it does when unboosted. The same also applies for opposing Pokémon with Defense or Special drops.


When a Pokémon is frozen in RBY, it will never thaw out unless the opponent uses a Fire-type move against the frozen Pokémon or uses Haze. This is also the main reason behind the Freeze Clause existing in RBY, as well as the incredibly high usage of Ice Beam and Blizzard.

Special Stat

Unlike later gens, where Pokémon have a Special Attack and Special Defense stat, RBY only has the Special stat, which means that moves such as Psychic and Amnesia drop and raise Special as a whole, respectively.

Trapping Moves

When hit by either Wrap, Fire Spin, Bind, or Clamp, your Pokémon is made incapable of moving for 2-5 turns, which means that faster trappers can keep slower Pokémon constantly trapped, assuming the move doesn't miss. When a Pokémon switches out, the trapping sequence restarts and it uses up an extra PP. If the trapping move has 0 PP when an opposing Pokémon switches in, the PP counter will roll over to 63.

1/256 Chance

Because of the way RBY mechanics work, every move in the game with 100% accuracy apart from Swift has a 1/256 chance (or just under 0.4%) to miss. This applies similarly to critical hits, where a fast user of a high critical hit rate move, such as Persian, will have a 1/512 chance to not land a critical hit.


When a Pokémon is put to sleep by Sleep Powder or Hypnosis, they can sleep for 0-6 turns, meaning that they can potentially wake up the turn they were put to sleep. Waking up from sleep uses up a turn in RBY, which means that a faster sleep inducer can keep a slower Pokémon permanently under sleep status, unless Sleep Powder or Hypnosis misses. An example of this could be Exeggutor against Slowbro.

Toxic (+ Leech Seed)

Toxic reverts to regular poison after a Pokémon switches out. Poison and Leech Seed only deal 1/16 damage to the opposing Pokémon instead of 1/8. When a Pokémon is under the effect of Leech Seed and Toxic, the damage dealt to it will increase extremely quickly, as Leech Seed deals more damage when in conjunction with Toxic. For instance, Toxic will deal 1/16 damage when first inflicted and Leech Seed will deal 2/16; this stacks further and by the fifth turn, the combined effect of Toxic and Leech Seed will be enough to OHKO the opposing Pokémon.


Paralysis reduces Speed to 1/4 of the Pokémon's initial Speed and has a 25% chance to fully paralyze the Pokémon, which has remained the same throughout all of Pokémon. However, in RBY, the paralysis Speed drop can be avoided by using Agility when the Pokémon has been paralyzed.

When a Pokémon is paralyzed, you can lower their Speed stat to 1 by changing your own Pokémon's stats while the opponent's Pokémon is paralyzed. This means you can use Thunder Wave on your opponent's Pokémon with Slowbro, which will quarter the foe's Speed, and then use Amnesia the following turn. The more you use Amnesia, the more the foe's Speed will drop until it reaches 1. The same also applies with burns and lowering the foe's Attack stat to 1.

Stat cap

In RBY, no matter what, the maximum stat a Pokémon can reach is 999. This means that Mewtwo only needs two Amnesia boosts to be at maximum Special.

Type Changes

Ice-type attacks deal neutral damage to Fire-types instead of not very effective. This means that Moltres takes 2x damage from Ice Beam and Blizzard instead of 1x. Poison-type moves are super effective against Bug-types instead of neutral, while Bug-type moves are super effective against Poison-types instead of not very effective. Psychic-types are immune to all Ghost-type attacks apart from Night Shade.

Recovery moves failing

When a Pokémon is 255 or 511 HP below its maximum HP, any recovery move such as Rest, Soft-Boiled, or Recover will fail. This means that a Slowbro at 138 HP will fail to use Rest, as 393 - 255 = 138.

Secondary effects

Moves with secondary effects cannot affect Pokémon of the same type, meaning that Normal-types cannot be paralyzed by Body Slam, Electric-types can't be paralyzed by Thunderbolt, Ice-types can't be frozen by Ice Beam and Blizzard, and Fire-types cannot be burned by Fire Blast. This mechanic was recently discovered and the change to Body Slam had a huge effect on the metagame, as it made Rock-types less viable because they couldn't fulfill their roles of handling Normal-types as effectively.

Major Move Changes

Counter: Counter will fail if the foe's last used move has a Base Power of 0 or is a non-attacking move, or if the foe's last used move is not Normal- or Fighting-type, aside from Counter, and if Counter goes first.

It is possible to Counter a previous Counter if the foe does not use a PP the following turn, and the same applies to Explosion. The Pokémon that uses Counter does not have to be the Pokémon that takes damage from the foe. Counter still deals 2x damage as per usual.

Dig and Fly: When a Pokémon is fully paralyzed the turn they are in the ground or in the air, it will be immune to all attacks apart from Swift, Bide, and Transform. The Pokémon is still able to use their other moves when invincible, hence why the moves Dig and Fly are banned in competitive RBY.

Hyper Beam: Hyper Beam does not need to recharge if it KOes an opposing Pokémon, breaks a Substitute, or misses. This makes for an extremely spammable move late-game in RBY and is what makes attackers such as Tauros so threatening. During the recharge turn, if the opponent uses a sleep-inducing move, it cannot miss and will overwrite any other status.

Substitute: The only status condition that Substitute blocks is poison, meaning that moves such as Thunder Wave and Sleep Powder are capable of hitting through a Substitute. Explosion and Self-Destruct also do not KO the user if the user Explodes against a Substitute.

Rest: When a Pokémon is afflicted with a status condition such as burn or paralysis and uses Rest, they will not regain their lowered stats until they switch out. This means that a paralyzed Slowbro will remain at 39 Speed until it switches out.

Reflect and Light Screen: Reflect and Light Screen will permanently reduce the damage taken from the opposing team's attacks until the user switches out, though this only affects a single Pokémon and doesn't affect the entire team unlike in later generations. Critical hits also bypass Reflect and Light Screen, which can also be removed by using Haze.

Minor Move Changes

Blizzard: Blizzard has 90% accuracy in RBY as opposed to 70%.

Explosion and Self-Destruct: Explosion's Base Power is 170, down from 250, while Self-Destruct is 130 BP, down from 200. Both attacks halve the opponent's Defense, a mechanic that remained until BW.

Mimic: Mimic will copy a random move from the opponent's Pokémon when used, unlike in later gens where it copies the last move used.

Disable: Disable works similarly to Mimic, but it disables a random move on the opponent's Pokémon instead of the last one used.

Fire Blast: Fire Blast has a 30% chance to burn, up from 10%. Burns also deal 1/16 HP instead of 1/8 HP.

Thunder: Thunder only has a 10% chance to paralyze, rather than 30% in later generations.

Seismic Toss and Night Shade: Even though Seismic Toss and Night Shade are Fighting- and Ghost-type moves, respectively, they are capable of hitting Pokémon immune to them, meaning that Seismic Toss can damage Ghost-types and Night Shade can damage Normal- and Psychic-types.

Rage: Upon using Rage, the Pokémon will stop obeying the trainer and will not stop using Rage until it faints. Rage's accuracy is affected in weird way when it misses due to evasion / accuracy modifiers, which is best explained by this post.

Focus Energy: Focus Energy doesn't increase the critical hit ratio; it quarters it instead. This was fixed in Pokémon Stadium, but cartridge mechanics are used more often.

Whirlwind and Roar: These moves have absolutely no use in trainer battles, which literally makes them the worst and most useless moves in the game.

Multi-hit moves: The first hit in a multi-hit attack determines if any follow-up hit will be a critical hit. If the first hit of Double Kick or Twineedle is a critical hit, the next hit will also be a critical hit.

« Previous Article Home Next Article »