Personality value

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Revision as of 02:37, 29 June 2015 by Goukazaru (talk | contribs) (The description of the determination of gender is somewhat confusing, so I added a pseudocode description of the algorithm.)
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A Pokémon's personality value is an unsigned 32-bit integer that is created when the Pokémon is first encountered. It is set when a Pokémon appears in the wild, when an Egg is first received from the Pokémon Day Care by the player (in Generation III* except in Pokémon Emerald and in Generation V) or by the Day-Care man (in Emerald and Generation IV), or when a Pokémon or its Egg is received from an NPC. As an unsigned 32-bit integer, its value can be anywhere from 0 (32 zeroes in binary) to 4,294,967,295 (32 ones in binary), inclusive. This value was introduced with the Pokémon data structure overhaul that occurred at the start of Generation III, and is generated using the games' pseudorandom number generator.


00000000 00000000 00000000 00000000

A Pokémon's gender is determined by the lowest eight digits (the lowest byte, highlighted in red above) of p in binary form. Mathematically, this can be derived by calculating p % 256. Below, this value will be referred to as pgender.

In a Pokémon species' base stat structure, there is a value called the gender threshold, a byte with a value ranging from 0 to 255. Genderless species of Pokémon such as Magnemite have a value of 255 for their gender threshold. Female-only species such as Nidoran♀ have a value of 254 for their gender threshold, while for male only species such as Nidoran♂ the value is 0. The remaining values describe Pokémon with both genders: if pgender is greater than or equal to the gender threshold, the Pokémon is male; otherwise it is female.

Gender threshold Gender ratio
Binary Decimal Male Female
11111111 255 Genderless
11111110 254 0.0% 100.0%
11011111 223 12.5% 87.5%
10111111 191 25.0% 75.0%
01111111 127 50.0% 50.0%
00111111 63 75.0% 25.0%
00011111 31 87.5% 12.5%
00000000 0 100.0% 0.0%

Because the comparison to determine gender is greater than or equal, Pokémon are not actually perfectly distributed between male and female according to the ideal ratios shown above. For example, for a Pokémon with a 50/50 male/female gender ratio, there is actually a 129/256 (50.390625%) chance for the Pokémon to be male and 127/256 (49.609375%) chance for the Pokémon to be female.


procedure gender(p_value, threshold):
  if threshold = 255: return GENDERLESS
  if threshold = 254: return FEMALE
  p_gender := p_value & 0xFF
  if p_gender < threshold: return FEMALE
  else: return MALE


Generation III-IV origin: 00000000 00000000 00000000 00000000
Generation V origin: 00000000 00000000 00000000 00000000

In Generations III and IV, if a Pokémon's species has more than one Ability, its Ability is determined by the lowest bit (highlighted in red above) of its personality value; i.e., whether p is even or odd. If p is even (the lowest bit is 0), the Pokémon has its first Ability. If p is odd (the lowest bit is 1), it has the second.

In Generation V, a Pokémon's Ability is determined differently depending on whether it originated in Generation V or an earlier generation. Pokémon from earlier generations will still have their Ability determined by the lowest bit in p. Pokémon originating in Generation V, however, use the lowest bit of the upper half of p to determine their Ability. Just as with Generation III and IV Pokémon, a 0 still indicates a Pokémon's first Ability, while 1 indicates its second. This can be derived by calculating p / 65536 % 2 (rounded down).

If a Pokémon is transferred to a later generation where its species' Abilities have changed, it will retain the Ability it had in the earlier generation so long as it does not evolve, since the games store a Pokémon's current Ability in a value separate from its personality value. However, in Generations IV and V, when a Pokémon evolves, its personality value is rechecked and the Pokémon's Ability may change. If a Pokémon that would change Abilities on evolution is transferred to Generation VI, it will be locked into its current Ability slot upon transfer through Poké Transporter.

As an example, in Generation III, Porygon and Porygon2 only had the Ability Trace, but in Generation IV, they gained Download as a second Ability. If a Porygon from Generation III is brought to a Generation IV game, it will have Trace no matter what its personality value; however, if it evolves into Porygon2, it will only keep Trace if p is even.

A separate bit governs whether a Pokémon has their normal Abilities or Hidden Abilities in Generation V. If a Pokémon has its Hidden Ability, its personality value is always set to be even (denoting a first Ability), so as to allow the inclusion of a second Hidden Ability in a future generation.[citation needed]

Nature (Generation III and IV only)

In Generations III and IV a Pokémon's Nature is determined by p % 25. From Generation V onward, Nature is determined by a separate byte, unrelated to the personality value.

The result of p % 25 corresponds to the following Natures:

p % 25 Nature
0 Hardy
1 Lonely
2 Brave
3 Adamant
4 Naughty
5 Bold
6 Docile
7 Relaxed
8 Impish
9 Lax
10 Timid
11 Hasty
12 Serious
13 Jolly
14 Naive
15 Modest
16 Mild
17 Quiet
18 Bashful
19 Rash
20 Calm
21 Gentle
22 Sassy
23 Careful
24 Quirky


00000000 00000000 00000000 00000000

In Generation III or later, whether a Pokémon is Shiny depends on its Original Trainer's Trainer ID number and secret ID number and on the Pokémon's personality value. The high half of p (highlighted in red above) is referred to as p1 below, while the low half (highlighted in blue) is referred to as p2. Mathematically, p1 can be derived by calculating p / 65536 and rounding down the result, while p2 can be derived by calculating p % 65536.

S = IDTrainer IDSecretp1p2

A bitwise exclusive or operation (or "⊕") on inputs a and b, written as ab = c, outputs c such that, if ai (bit i of a) and bi are different, then ci is 1; otherwise it is 0. For example, 11002 ⊕ 10102 = 01102. When exclusive or is applied to multiple inputs, as in the calculation for Shininess above, it may be more easily understood as, "If an odd number of bits (at position i) are 1, output 1". This operation is commutative.

From Generations III to V, if S < 8, the Pokémon is Shiny. In Generation VI, the Pokémon is Shiny if S < 16. This is an 8 or 16 in 65536 chance of a Pokémon being Shiny.


As an example, given a Trainer whose Trainer ID is 24294 and whose Secret ID is 38834...

IDTrainer = 2429410 = 01011110111001102
IDSecret = 3883410 = 10010111101100102

If the Trainer encounters a Pokémon whose personality value is 2814471828...

p = 281447182810 = 101001111100000101101110100101002
p1 = 10100111110000012
p2 = 01101110100101002

Then S is equal to...

S = 01011110111001102 ⊕ 10010111101100102 ⊕ 10100111110000012 ⊕ 01101110100101002
S = 00000000000000012 = 110

Since S is less than 8, this Pokémon is Shiny.


From Generation IV onward, Pokémon have a Characteristic which indicates their highest IV. In the case of a tie, the personality value is used to determine which stat wins the tie.

The tie-breaker starts at the stat with the index p % 6 and increments the index (returning to 0 after reaching 5) if it is not one of the stats that is tied for highest. The first stat checked that is tied for highest wins the tie and will determine the Characteristic.

p % 6 Stat
0 HP
1 Attack
2 Defense
3 Speed
4 Special Attack
5 Special Defense

Spinda's spots

00000000 00000000 00000000 00000000

Spinda has four spots: two on its face, and one on each of its ears. Each byte in the personality value represents the coordinates of one of these spots. The x-coordinate is the lower four bits of the byte and the y-coordinate is the higher four bits of the byte. These coordinates determine the position of the top-left corner of the corresponding spot.

While this would appear to mean that Spinda's spots have as many possible variations as there are personality values (4,294,967,296), some coordinates will place a spot off of Spinda's body or such that one wholly overlaps another. Therefore, in practice, the number of observed variations is fewer.

Unown's letter (Generation III only)

00000000 00000000 00000000 00000000

pletter = 00000000

In Generation III, Unown's letter is determined by the composite value of the least significant 2 bits of each byte in p. With A representing 0 and each letter thereafter representing the following number value (with ? as 26 and ! as 27), Unown's letter can be determined by:

α = pletter % 28

In Generation II, this is determined using individual values. In Generations IV and V, Unown's letter is determined by a separate byte, unrelated to the personality value.

Wurmple's evolution

Generations III and IV: 00000000 00000000 00000000 00000000
Generation V: 00000000 00000000 00000000 00000000

Wurmple's evolution is determined by the lower half of its personality value in Generations III and IV or the upper half in Generation V (highlighted in red above), referred to here as pw. Mathematically, pw can be derived by calculating p % 65536 for Generations III and IV or p / 65536 (rounded down) for Generation V.

If the result of pw % 10 is less than 5, Wurmple will evolve into Silcoon. If it is greater than or equal to 5, Wurmple will evolve into Cascoon.


00000000 00000000 00000000 00000000

In Generations III and IV, there are occasionally characters who want to see large Pokémon. The calculation to determine the size of one of these Pokémon depends on its individual values and its personality value. Like the Shininess calculation, this calculation also uses exclusive or (⊕).

The lowest two bytes of p are used in the calculation: p1 (highlighted in blue above) is mathematically equivalent to p % 256, while p2 (highlighted in red) is equivalent to (p / 256) % 256 (rounded down). The IV values are also not used in whole; only the first four bits of each are used: mathematically, <stat>' = IV<stat> % 16.

The first step in the calculation is as follows:

s = ( ( (Atk'Def') * HP' ) ⊕ p1 ) * 256 + ( ( (SpAtk'SpDef') * Spd' ) ⊕ p2 )

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.

s (max): 9 109 309 709 2709 7709 17709 32709 47709 57709 62709 64709 65209 65409 65535
x 290 300 400 500 600 700 800 900 1000 1100 1200 1300 1400 1500 1700
y 1 1 2 4 20 50 100 150 150 100 50 20 5 2 1
z 0 10 110 310 710 2710 7710 17710 32710 47710 57710 62710 64710 65210 65510

The final part of the calculation gives the Pokémon's size in millimeters. The final value of Size is also rounded down.

Size = Rounddown( (s-z) / y + x ) * h / 10

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:

Performance changes

00000000 00000000 00000000 00000000

The day-to-day performance of a Pokémon in the Pokéathlon depends on its personality value and the day of the month. It also depends on Nature, which is also calculated based on the personality value. The five least significant digits of p will here be referred to as p0 to p4, in order from the least significant bit to the most significant, and they govern (in order) the attributes Power, Stamina, Skill, Jump, and Speed.

The change in performance in a particular attribute is calculated as the sum of the following factors:

  • Day of the month modifier: ( ( (day + attribute + 3) × (day - attribute + 7) + pattribute ) % 10 ) × 2 - 9, where:
    • Day is the day of the month.
    • Attribute is 0 for Power, 1 for Stamina, 2 for Skill, 3 for Jump, and 4 for Speed.
    • pattribute is the bit of p governing the current attribute.
Note that this modifier's values range from -9 to +9, and it only takes on odd values. This also means that the day of the month modifier cycles every 10 days, excepting for Power and Speed where the modifiers for Day 1 are different from those for Days 11, 21, and 31.
Since Nature is determined by the last two digits of the personality value, the Nature of a Pokémon will reveal constrains on possible values of this modifier for Power (and, to a lesser extent, Stamina). For example, a Hardy Wurmple (last digit of p: 0 or 5) will never get a +9 or a +7 from this modifier in Power. If it evolves into a Cascoon (last digit of p: 5), this further reveals that its best day-of-the-month modifier (+5) will be on the first day of a month only. On the other hand, a Hardy Silcoon will have a +5 boost six times a month (on days ending with 4 or 6).
  • Nature modifier: the Pokémon's Nature may raise or lower its performance in an attribute. Non-neutral Natures will add or subtract 35 points from an attribute, if the Nature positively or negatively influences the stat that corresponds to the current attribute. Neutral natures will add or subtract 10 points from an attribute depending on the Nature.
Attribute Neutral +10 Neutral -10 Non-neutral stat (+/- 35)
Power Hardy Bashful Attack
Stamina Docile Quirky Defense
Skill Quirky Serious Sp. Def
Jump Bashful Docile Sp. Atk
Speed Serious Hardy Speed
  • Aprijuice modifier: the last Aprijuice the Pokémon drank affects the Pokémon's performance, depending on the strengths of the flavors in the Aprijuice.
    • Strongest flavor: add flavor * 1.5 (rounded down) plus 10 to the corresponding attribute.
    • Second strongest flavor: add flavor * 1.5 (rounded down) to the corresponding attribute.
    • Weakest flavor: subtract X times the sum of the two strongest flavors (rounded down) from the corresponding attribute, depending on the Aprijuice's mildness...
      • 0 - 199: X = 1 - 0.1 * Rounddown( mildness / 25 )
      • 200-254: X = 0.2
      • 255: X = 0.1
The Aprijuice flavors correspond to the performance attributes as follows:
Flavor Attribute
Spicy Power
Sour Stamina
Dry Skill
Bitter Jump
Sweet Speed

The sum of these modifiers is then translated into a difference in stars as follows:

Stars -4 -3 -2 -1 0 1 2 3 4
Score ...-120 -119...-80 -79...-40 -39...-15 -14...14 15...39 40...79 80...119 120...

Note that performance changes may not drop below the Pokémon's minimum performance rating, nor may it exceed the Pokémon's maximum performance rating. Thus, for example, a Cradily may never have its Speed or Jump rating improved or degraded as those attributes are fixed (as such, for example, it is advisable to give it dry Aprijuices for which sweetness or bitterness is its weakest flavor).

Other uses

A Pokémon's personality value may also used for things unrelated to the Pokémon itself.

In Pokémon Ruby, Sapphire, and Emerald, Mirage Island will appear on Route 130 if the lower half of the personality value of a Pokémon in the player's party matches a random number generated at the start of each day by the game. A man in Pacifidlog Town can also tell the player whether he sees the island "today", i.e., whether one of the Pokémon in the player's party matches Mirage Island's number.

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