Why is a perfect IV Pokemon no longer 'perfect' after evolution/powering up in Pokemon Go?

I had a Shellder that I calculated on 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

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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 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.

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3 Answers

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.

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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)

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