Size and weight variation

Size and weight variation is a mechanic where multiple Pokémon of the same species can vary in both size and weight.

In the core series

Generations III and IV

In Generations III and IV there are occasionally NPCs who want to see large Pokémon. The calculation used to determine the size of one of these Pokémon depends on its individual values and its personality value, which is a 32 bit integer created when a Pokémon is first generated.

00000000 00000000 00000000 00000000

The lowest two bytes of p are used in the calculation: p₁ (highlighted in blue above) is mathematically equivalent to p mod 256, while p₂ (highlighted in red) is equivalent to ${\displaystyle \lfloor p/256\rfloor {\bmod {2}}56}$. The IV values are also not used in whole; only the four least significant bits of each are used: mathematically, <stat>' = IV<stat> mod 16.

The first step in the calculation is as follows:

${\displaystyle s=256\cdot (p_{1}\oplus (HP'\cdot (Atk'\oplus Def')))+(p_{2}\oplus (Spd'\cdot (SpAtk'\oplus SpDef')))}$

For the next step, h is the species' height in tenths of a meter. and the values of x, y, and z depend on the value of s as shown in the following table.

The final part of the calculation scales the s value to produce the Pokémon's size in millimeters. The final value of Size is bounded between 0.29 and 1.725 times the standard height given for the species in the Pokédex, and rounded down.

${\displaystyle Size=\left\lfloor {\frac {h\cdot \left\lfloor {\frac {s-z}{y}}+x\right\rfloor }{10}}\right\rfloor }$

If the game converts this number to inches, the final result will be rounded down to the nearest tenth of an inch.

The characters searching for large Pokémon can be found at the following locations:

Generation VII

Sun, Moon, Ultra Sun, and Ultra Moon

Totem Pokémon are a special kind of Pokémon that are much larger and heavier than their standard counterparts. They are battled at the end of every trial, having been trained up by the respective Trial Captain to fulfill that role. Their increased weight can influence the mechanics of some moves (such as Low Kick and Sky Drop).

Pokémon		Introduced	Height		Weight		Ability
	Alolan Raticate	SM	4'07"	1.4 m	231.5 lbs.	105.0 kg	Thick Fat
	Alolan Marowak	USUM	5'07"	1.7 m	216.1 lbs.	98.0 kg	Rock Head
	Gumshoos	SM	4'07"	1.4 m	132.3 lbs.	60.0 kg	Adaptability
	Vikavolt	SM	8'06"	2.6 m	325.2 lbs.	147.5 kg	Levitate
	Ribombee	USUM	1'04"	0.4 m	4.4 lbs.	2.0 kg	Sweet Veil
	Araquanid	USUM	10'02"	3.1 m	479.5 lbs.	217.5 kg	Water Bubble
	Lurantis	SM	4'11"	1.5 m	127.9 lbs.	58.0 kg	Leaf Guard
	Salazzle	SM	6'11"	2.1 m	178.6 lbs.	81.0 kg	Corrosion
	Togedemaru	USUM	2'00"	0.6 m	28.7 lbs.	13.0 kg	Sturdy
	Mimikyu	SM	1'04"	0.4 m	6.2 lbs.	2.8 kg	Disguise
	Kommo-o	SM	7'10"	2.4 m	457.5 lbs.	207.5 kg	Overcoat

In Pokémon Ultra Sun and Ultra Moon, the player is able to obtain Totem-sized Pokémon from Samson Oak at Heahea Beach after meeting him for the first time at Route 2, based off of how many Totem stickers the player has obtained. Their size cannot be passed down through Pokémon breeding. Totem-sized Pokémon that originally appeared as Totem Pokémon in Pokémon Sun and Moon are the only ones that can be traded to the original Sun and Moon games and deposited in Pokémon Bank. Totem-sized Pokémon based on Totem Pokémon that only appear in Ultra Sun and Ultra Moon cannot be deposited in Pokémon Bank or traded to the original Sun and Moon games.

Totem-sized Pokémon that are transferred to Pokémon HOME are turned into their normal-sized forms.

Number of Totem Stickers	Pokémon
	Ultra Sun	Ultra Moon
20
40
50
70
80
100

Let's Go, Pikachu! and Let's Go, Eevee!

Unlike in previous games, every Pokémon in Pokémon Let's Go, Pikachu! and Let's Go, Eevee!, can vary in both height and weight. The height and weight from previous Pokédex entries are used as species average height and weight. From there, a Pokémon's height can vary as much as ±40% and their weight can vary as much as ±68%. Additionally, the Pokédex will keep track of the tallest, shortest, heaviest, and lightest Pokémon for every species the player has caught. These variation in height are not visible. Instead, large or small wild Pokémon will have a red or blue aura (respectively) around them, indicating their abnormal size. After being caught, a Pokémon's height and weight can be viewed in the summary screen.

A Pokémon's height and weight are determined by two separate 8 bit integers, or a value between 0 and 255. These values are obtained by generating two numbers, one between 0 and 127, and the other between 0 and 128. The numbers are then added together, which forms a triangular distribution that results in average sized Pokémon being more common. However, before the player enters Viridian Forest, the game will use a different formula. The game will generate a single number between 48 and 207, preventing large or small Pokémon from appearing until the player enters Viridian Forest.

The displayed height and weight are calculated as follows;
${\displaystyle Height({\text{meters}})=\left({\dfrac {\text{HeightInt}}{255}}\times 0.8+0.6\right)\times {\text{BaseHeight}}}$
${\displaystyle Weight({\text{kilograms}})=\left({\dfrac {\text{WeightInt}}{255}}\times 0.4+0.8\right)\times \left({\dfrac {\text{HeightInt}}{255}}\times 0.8+0.6\right)\times {\text{BaseWeight}}}$

Pokémon come in 5 size groups determined by height. XS, S, AV, L, and XL. The odd of encountering a Pokémon with more extreme height and weight values can be increased by building up a Catch Combo and using Lures. Using these methods will cause the game to reroll a Pokémon's height and weight values, saving whichever number is the closest to 0 or 255. Lures provide 1 additional roll, while the final tier of a catch combo can create 6 rolls. These rerolls can still occur before entering Viridian Forest but will never result in a large or small Pokémon.

Pokémon that are L, XL, S, or XS will receive a permanent 1.2x multiplier to any experience they receive. Catching a Pokémon that is XL or XS will grant the player a size bonus, which is a 4x multiplier to the experience earned that capture.

Generation VIII

Brilliant Diamond and Shining Pearl

Legends: Arceus

Generation IX

In side games

Pokémon GO