I had a Shellder that I calculated on https://thesilphroad.com/research and it was a perfect IV one. I evolved it into a Cloyster and powered him up, and checked the site again, and it is no longer a perfect IV Pokemon anymore - it has 2 CP less then a perfect one.

How can this happen? I did change the name to Cloyster IV to know that that was my Perfect one and after that I powered it up 2 times so maybe it gave me 1 cp less everytime I powered it up after I changed the name. Can someone help me please?

stats of the cloyster:

  • CP: 848
  • Powerup cost: 1600 dust, 2 candy
  • HP = 58

UPDATE! My Cloyster is now 877 and I figured out that each time I power it up it gets +29 cp, I used the site https://thesilphroad.com/research to do my calculating.

I checked the site and I began 877-29= 848 848-29=819...

Until I got to 703 the site said my Cloyster had an perfect IV. But after upgrading it to 877 the site said it wasn't perfect anymore. I now have checked some other sites and used the 703 stats and they also say it's a perfect IV but when I then give in the 877 stats it isn't perfect anymore.

  • 6
    You were mistaken. Aug 13, 2016 at 15:57
  • 3
    Your Cloyster never was perfect. Can you give us the rest of the numbers so we can reconstruct the issue? Your trainer level and the arc position you used, specifically. Did you make sure you always moved the arc the same number of times you powered up and double checked the upgrade cost every time?
    – scenia
    Aug 17, 2016 at 4:41

3 Answers 3


You likely used the wrong level value for calculating your IVs. Different sites handle this differently, but if you calculate it manually you would know that for each powerup cost, there are 2 possible odd levels (if the Pokemon is fresh, since wild Pokemon only show up at odd levels), and 2 possible even levels.

Either the IV calculator you used assumed it was at a lower level than it actually was, or you had previously powered it up, hence giving you an incorrect value when initially determining it was perfect.

Alternatively, if you powered it up an odd number of times after checking the IVs for the first time, it's possible that you or your IV calculator didn't account for it.

  • Today I caught a shellder and it gave me some candies so I powered my cloyster up another time with the name cloyster and not with his nickname, now I checked the site again and belioeve it or not now it just did a perect power up so I'm now still 2 cp away from the perfect cp :( so that means 2 times powered up with a nickname = -2 cp Aug 14, 2016 at 16:19
  • @Seppe: You're definitely calculating your initial IVs wrong. Powering up increases the Pokemon's level by 0.5, the stardust cost increases every 2 levels, so every 4 powerups. Many calculators assume you powered the Pokemon up until the stardust cost increased, which would mean it's at the lowest possible level for that cost, but if you didn't do that, the calculator will use the wrong level 50% of the time (whenever your caught Pokemon is one level above the level at which stardust cost increased; wild Pokemon never have half levels).
    – scenia
    Aug 17, 2016 at 4:32

The answer is rounding error. The CP and HP calculations are rounded down to the nearest integer, so when the numbers are small, perfect IV and almost perfect IV can give the same results. However as the numbers get bigger, which happens with powerups or evolutions, the rounding errors become less important and it's possible to distinguish perfect from almost perfect.

The IV levels for that pokémon are Attack=15, Defense=14, Stamina=15. I think about pokémon levels as numbers that go up in increments of 0.5, and in that scheme, dust=1600 corresponds to 4 possible levels 13, 13.5, 14 or 14.5. When the Cloyster CP was 848 it was at level 14.5. However, it must have been powered up a lot, because as a Shellder, its down at level 7 that perfect IV would have been indistinguishable from the almost perfect IVs for your pokémon.


It makes perfect sense that IV should change when powering up the way the game is set. With every power up all mons of the same type will get the same + in HP and CP no matter their IVs. So lets say you get a perfect one and the worst possible mon at lvl 2 and the difference in CP is 10 and HP is 2. If you power up both the same amount the difference in CP will always stay 10 and HP 2. However at higher levels the difference between higher and lower IVs is far greater then a mere 10/2 so unless the game powers up different IV mons differently then the IVs will have to change! (an example: lets say you get a perfect IV mon at lvl 2 and 30 CP 6 HP and the worst possible at 20 CP and 4 HP. Each power up gives 20 CP and 2 HP, after 100 power ups the perfect mon has 2030 CP and 206 HP the worst possible one 2020 CP and 204 HP. In the beginning the difference is massive, the more you power up the less relevant the difference and less different the IVs... (IMHO)

  • 6
    This is wrong. IVs are fixed and never change. Pokemon also get different amounts of CP and HP when powering up, depending on their IVs. The difference is small, so it won't be noticeable on many powerups, but there is a difference. Powering up increases the Pokemon's level by 0.5 and it's stats are then calculated based on species (base stats), IVs and level.
    – scenia
    Aug 17, 2016 at 4:26

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