Size and weight variation

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

In the core series games

Generation II

Histogram of size variation in Generation II

At the Lake of Rage, there is a Fishing Guru who requests to see large Magikarp after the player defeats Team Rocket at their hideout in Mahogany Town. The size of these Magikarp roughly follows a normal distribution, and depends on its individual values and its Original Trainer's Trainer ID number. If he is shown a Magikarp bigger than the previous record, he gives the player a prize; the initial record is 3'6" (105.3 cm). A Pokémon is considered to have beat the previous record if its calculated size in feet and inches (in millimeters in non-English games) is greater than the previous record.

Rates

In non-English games, large Magikarp are made rarer by regenerating the IVs of Magikarp that are 161.6 cm (5'3") or larger 95% of the time and Magikarp that are between 160.0 cm (5'2") and 161.5 cm (5'3") 76% of the time. Due to an oversight, these values were not properly converted to feet and inches in English-language games, meaning that they only attempt to regenerate the IVs of Magikarp that are 6'0" (182.9 cm) or larger; this has no effect, as no Magikarp can be that large.

Magikarp caught in the Lake of Rage were intended to be larger on average than Magikarp caught elsewhere, by regenerating the IVs of Magikarp that are 4'0" (122.0 cm) or smaller in English games or 102.4 cm (3'4") or smaller in non-English games or smaller 60% of the time. Due to a programming error, all Magikarp except for those in the Lake of Rage and Routes 20, 43, and 44 are larger on average, due to those maps having either the same map group (9) or map identifier (6) as the Lake of Rage.

The following table indicates the base probability of each size of Magikarp, ignoring rerolls and correlations between pseudorandom numbers.

Calculation

A rotate right carry (rrc) is performed on the 8 bits comprising the Attack and Defense IVs, the 8 bits comprising the Speed and Special IVs, and the 16 bits comprising the Trainer ID. After this, the two 8-bit values are concatenated to form a single 16-bit number, which is then XOR'd with the Trainer ID, as follows.

$${\displaystyle y=(256\cdot \operatorname {rrc} (IV_{1})+\operatorname {rrc} (IV_{2}))\oplus \operatorname {rrc} (ID)}$$

As a special case, if y < 10, then the Magikarp's length is equal to ${\textstyle 190+y}$. Otherwise, the value y is used to find the corresponding values of x₀, y₀, and m in the following table, which defines a piecewise linear approximation of the inverse of the normal cumulative distribution function. Due to a programming error, only the high bytes of y and y₀ are compared; this results in the first and last columns being inaccessible.

If one of the entries in the table matches, the final length of the Magikarp in millimeters is then calculated as follows. Due to a programming error, the function does not output ${\textstyle 100\cdot x_{0}+\left\lfloor {\frac {y-y_{0}}{m}}\right\rfloor }$ as intended. Because y is always less than y₀, the subtraction always results in a negative value; however, the division routine expects the dividend to be an unsigned 16-bit value. Additionally, only the low byte of the quotient is read, as the difference between y and y₀ was intended to only range from 1 to 100.

$${\displaystyle {\textit {Size}}=100\cdot x_{0}+\left(\left\lfloor {\frac {65536+y-y_{0}}{m}}\right\rfloor \mathrm {mod} \ 256\right)}$$

If none of the entries in the table match (because y ≥ 65280), the Magikarp's length is instead equal to ${\textstyle 1600+(y-y_{0})}$, where y₀ is 65510, the last entry for y₀ in the table.

If the game converts this number to feet and inches, the final result will be rounded down to the nearest inch.

Generations III and IV

Histogram of size variation in Generations III and IV

In Generations III and IV, there are occasionally NPCs who want to see large Pokémon. The size of these Pokémon follows a normal distribution, and is calculated from its individual values and its personality value. If shown a Pokémon that exceeds the previous record, the NPC will give the player a prize if it exceeds the previous record. A Pokémon is considered to have beat the previous record if its calculated size in millimeters (in all Generation III games and non-English Generation IV games) or its calculated size in tenths of an inch (in English-language Generation IV games) is greater than the previous record.

Locations

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

Calculation

Only the lowest two bytes of the personality value are used in the calculation: p₁ (highlighted in blue below) is the least significant byte, while p₂ (highlighted in red) is the second least significant byte.

00000000 00000000 00000000 00000000

Additionally, only the four least significant bits of each IV are used in the calculation: mathematically, ${\displaystyle {\textit {stat}}'={\textit {IV}}_{\textit {stat}}\mod 16}$.

The first step in the calculation is as follows:

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

For the next step, the value y is used to find the corresponding values of x₀, m, and y₀ in the following table, which defines a piecewise linear approximation of the inverse of the normal cumulative distribution function.

The values of x₀, m, and y₀ are then used to convert the uniformly distributed value y to the normally distributed value x.

$${\displaystyle x=x_{0}+\left\lfloor {\frac {y-y_{0}}{m}}\right\rfloor }$$

The final part of the calculation scales h (the species' height in tenths of a meter) by the x value to produce the Pokémon's size in millimeters. The size is bounded between 0.29 and 1.725 times the standard metric height for the species (as listed in the Pokédex), rounded down.

$${\displaystyle {\textit {Size}}=\left\lfloor {\frac {h\cdot x}{10}}\right\rfloor }$$

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

Generation VII

Pokémon Sun, Moon, Ultra Sun, and Ultra Moon

Main article: Totem Pokémon

In Pokémon Sun, Moon, Ultra Sun, and Ultra Moon, Totem Pokémon are a type of variant 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 their 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 on 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 Pokémon Sun and Moon games and deposited in Pokémon Bank. Totem-sized Pokémon based on Totem Pokémon that only appear in Pokémon Ultra Sun and Ultra Moon cannot be deposited in Pokémon Bank or traded to the original Pokémon Sun and Moon games.

Totem-sized Pokémon that are transferred to Pokémon HOME revert to their normal-sized forms and do not preserve their increased size.

Pokémon: 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 base height and weight. From there, a Pokémon's height can vary as much as ±40% and their weight can vary as much as +68% to -52%. Additionally, the Pokédex will keep track of the tallest, shortest, heaviest, and lightest Pokémon for every species the player has caught. These variations 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 values between 0 and 255, the height scalar and weight scalar respectively. 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.^[1] 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,^[2] preventing large or small Pokémon from appearing until the player enters Viridian Forest.

The displayed height and weight are calculated as follows;
${\displaystyle Height_{m}=\left({\dfrac {\text{HeightScalar}}{255}}\times 0.79999995+0.6\right)\times {\text{BaseHeight}}}$
${\displaystyle Weight_{kg}=\left({\dfrac {\text{WeightScalar}}{255}}\times 0.40000004+0.8\right)\times \left({\dfrac {\text{HeightScalar}}{255}}\times 0.79999995+0.6\right)\times {\text{BaseWeight}}}$

The game will then convert height to feet and inches, and weight to pounds.

Pokémon come in five size groups determined by height: XS, S, AV, L, and XL. The odds of encountering a Pokémon with more extreme scalar 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 scalar and weight values, saving whichever number is the furthest from 128. Lures provide 1 additional roll, while the final tier of a catch combo can create 6 rolls.^[3] 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 1.2× multiplier to any experience they receive. Catching a Pokémon that is XL or XS will grant the player a size bonus, which is a 4× multiplier to the experience earned that capture.

Generation VIII

Pokémon Sword and Shield

While Pokémon Sword and Shield generate individual height and weight scalar values the same way as before, these values go unused unless transferred to a game that supports them.

Pokémon Brilliant Diamond and Shining Pearl

While Pokémon Brilliant Diamond and Shining Pearl generate individual height and weight scalar values the same way as before, these values go unused unless transferred to a game that supports them.

Once again, a Fisherman on Route 222 can be shown Remoraid, and will judge their height. The game uses the same calculation from Generation III and IV, only substituting the Pokémon's Personality value for its Encryption constant.

Pokémon Legends: Arceus

Pokémon once again vary in both height and weight in Pokémon Legends: Arceus, and variations in height are now visible in game. Height now varies by ±20%, and weight now varies by +44% to -36%.

${\displaystyle Height_{m}=\left({\dfrac {\text{HeightScalar}}{255}}\times 0.40000004+0.8\right)\times {\text{BaseHeight}}}$
${\displaystyle Weight_{kg}=\left({\dfrac {\text{WeightScalar}}{255}}\times 0.40000004+0.8\right)\times \left({\dfrac {\text{HeightScalar}}{255}}\times 0.40000004+0.8\right)\times {\text{BaseWeight}}}$

Additionally, alpha Pokémon appear as much larger versions of normal Pokémon. Every alpha Pokémon has their height scalar and weight scalar values automatically set to 255. From there, height and weight receive an additional multiplier. This multiplier is unique for every species, and in some cases, like Basculegion, this multiplier may even be 1×.

This section is incomplete. Please feel free to edit this section to add missing information and complete it. Reason: What are the height/weight thresholds for each research task? Thresholds vary with each task. What is the multiplier for each species?

Several Research tasks may require the player to catch tall, short, heavy, and light specimens. Because alpha Pokémon have both scalars set to 255, they will always count as tall and heavy for the research task.

Pokémon sent from Pokémon Bank to Pokémon HOME did not come with scalar values. Prior to May 29, 2023 (the release of Pokémon HOME v3.0.0), if a Pokémon without a scalar value was transferred to Pokémon Legends: Arceus, it was assigned the minimum possible scalar value of 0. Starting on May 29, 2023 with the release of Pokémon HOME v3.0.0 (which added compatibility with Pokémon Scarlet and Violet), any Pokémon without a scalar value that is transferred to Pokémon Legends: Arceus, Scarlet, or Violet instead is given a randomly-generated scalar value, generated according to the triangular distribution that is used in Pokémon Scarlet and Violet. Pokémon that had already been assigned a scalar value by visiting Pokémon Legends: Arceus before the release of Pokémon HOME keep their scalar value.

Height and weight locked Pokémon

The following Pokémon are height and weight locked, and when caught, will always have a scalar value of 127. If any of the following Pokémon have a value other than 127 such as by transferring one in from a different game, it's in game model will always look as if its height scalar is 127. The Pokédex and summary screen will still reflect their true values.

Due to an oversight, Phione's scalar values are not locked when spawned in game.

Generation IX

Pokémon Scarlet and Violet

While Pokémon Scarlet and Violet generate individual height and weight scalar values the same way as before, these values go unused unless transferred to a game that supports them. Instead, a new scale value is used to replace height scalar, and is generated with the same triangular distribution. Height can vary as much as ±20%, and weight no longer varies at all.

Pokémon come in several size groups, and their scale can be judged by a Hiker next to the West Mesagoza Pokémon Center. If the player shows off a Pokémon with a scale of 255 or 0, the Hiker will give that Pokémon a Jumbo or Mini Mark, respectively.

The scale of a Pokémon can be influenced by Meal Powers, with Humungo Power increasing the odds of finding large Pokémon, and Teensy Power increasing the odds of finding small Pokémon. This is done by limiting the scale range of any Pokémon spawns that match the Meal Power's type. Instead of generating two values and adding them together, Meal Powers will only generate a single random number in that range. If a Pokémon is affected by both a Humungo and Teensy power at the same time, its Scale can generate in either range.^[4]

Humungo and Teensy Power will only affect wild Pokémon, and will not influence Pokémon hatched from Eggs, caught in raids, or received as gifts. The scale of Pokémon hatched from Eggs is generated like normal and is unaffected by the scale of their parents. Wild Tera Pokémon will always spawn from a scale of 200 to 255 with a uniform distribution. Former Titan Pokémon will always have a set scale of 255.

Versions 1.0 & 1.1

Versions 1.2+

In the version 1.2 update, the ranges for each size classification was changed, likely to make the ranges even. Pokémon received via Mystery Gift can now be of a specified scale. If the gift Pokémon does not have a specific scale, their scale will no longer be generated using a triangular distribution. Instead their scale will be randomly selected between 0 and 255,^[5] greatly increasing the chance that they generated a more extreme scale value.

Lock on upgrade

In the League Club Room at Blueberry Academy, the player can purchase an upgrade for their lock on feature from the Photography Club for 200 BP. Once upgraded, whenever the player locks onto a wild Pokémon with ZL, two different icons can appear next to the targeted Pokémon's name if their scale is less than 59 or greater than 196.^[6]

Scale locked Pokémon

The following Pokémon are scale locked, and when caught, will always have a scale value of 128. If one of the following Pokémon has a scale value other than 128, which may occur if it were transferred from a different game, its in-game model will always appear as if its scale is 128. The Hiker in Mesagoza will still judge Pokémon based on their true scale value, meaning it is still possible for these Pokémon to receive a Jumbo or Mini Mark.

In the spin-off games

Pokémon GO

This section is incomplete. Please feel free to edit this section to add missing information and complete it. Reason: More in-depth information such as how the weight is determined is not presented (can be found in the reference).

In Pokémon GO, there are five size classes: XXS, XS, M (only used internally), XL, and XXL.^[7]

The XXL class's upper bound can be either 155%, 175% or 200% depending on species. Scatterbug's lower bound for XXS is 25% instead of 49%.

Pumpkaboo and Gourgeist are instead assigned height classes based on their form: Small Size is XS, Average Size is M, Large Size is XL, and Super Size is XXL. Mega-Evolved Pokémon have their height class calculated relative to their species' height, so often display as being a different height class to their base form.

Connection with other games

Pokémon from Pokémon GO retain their size when transferred into Pokémon: Let's Go, Pikachu! and Let's Go, Eevee! or Pokémon HOME. Additionally, if the Pokémon is XXL size in GO, it will be guaranteed to have a Scale value of 255, and XXS will receive a Scale value of 0.

Upon the release of Pokémon HOME v3.0.0 on May 30, 2023, there was a bug where XXS size GO Pokémon received a random Scale value when sent directly to HOME, randomizing the size values in the same manner as any other Pokémon with Height/Weight values of 0/0. This was resolved server-side sometime on or before June 15, 2023.^[8]

Pokémon Sleep

This section is a stub. You can help Bulbapedia by expanding it.

In Pokémon Sleep, each Snorlax grows larger when it advances rankings. It begins at its smallest size at Normal, grows larger twice as it gets to Great and Ultra, and reaches its maximum size when it gets to Master.

See also

• Giant Pokémon

References

This game mechanic article is part of Project Games, a Bulbapedia project that aims to write comprehensive articles on the Pokémon games.