Once you've started collecting enough Pokémon, you'll want to turn your attention to evolving and Powering Up to discover new creatures and make them strong enough to defend and capture Gyms. It's a surprisingly complicated decision to make, now that we know more about how complex Pokémon Go can be, so we'll start at the beginning by explaining how the evolution process works and what you should be paying attention to, before talking about when you should evolve and when you should Power Up those Pokémon.
The higher the CP, the more powerful a Pokémon will be in battle. As you play and collect Pokemon, you'll discover that not every capture has the same CP level. You can read on what CP means in Pokemon Go and how to get the highest values for your team, but in short, CP is one of the most important factors when it comes to fighting, and aside from collecting it's likely the driving force behind your desire to Power Up or evolve.
Because of those complexities surrounding your Pokémon's CP, Powering Up and evolving is more than just a case of picking the one with the highest CP and throwing your Stardust and Candy at it until you run dry. As you'll see below, sometimes you should Power Up your Pokémon first, sometimes you should evolve it first, sometimes both, and sometimes you should leave it alone.
How to evolve Pokémon and how to Power Up
Powering up and evolving Pokémon requires in-game resources known as Stardust and Candy. Stardust is a shared resource you receive for each Pokémon you catch, for storing Pokémon at Gyms and leveling up, while Candy is an item specific to that species - so Pikachu Candy, Pidgey Candy and so on. We've assembled some quick tips on how to get Candy in Pokémon Go here, plus how to get Stardust easily to strengthen your Pokémon.
In short, the more Pokémon of one type you catch, the more Candy you get to power up and evolve that species in its family, so it's well worth catching those low level Pidgeys to get that eventual Pidgeot evolution. Remember you can use in-game radar to locate and catch the Pokemon nearby, as well as discover Pokemon Type by location using real-world habitats.
Pokémon Go - Powering Up
There are several important points worth bearing in mind for when you're looking to Power Up your Pokémon:
Powering Up a Pokémon raises its CP - but a Pokémon's CP only indicates its strength right now, and doesn't take into account a Pokémon's potential. It might just have a higher CP because it's a higher Level.
So, it's the Pokémon with the highest potential CP that you want to spend your resources Powering Up, not necessarily the one that has the highest CP right now.
A Pokémon's potential is indicated by its IVs - hidden stats, given at random to each individual Pokémon you catch. You can check them using an IV calculator such as this.
The white bar above your Pokémon indicates how close it is to its maximum Level. Powering Up pushes the white bar along its arc by raising your Pokémon's Level - which caps out at 1.5 Levels above your own current Trainer Level, with the cap increasing as you Level up.
With the Stardust and Candy costs increasing significantly for higher-Level Pokémon, you'll soon find it's awfully expensive to Power Up a Pokémon to its maximum strength from a very low CP.
Pokémon Go - Evolution
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As with Powering Up, there are some important things to bear in mind for evolving your Pokémon.
Evolving is one of the main ways you can earn a large amount of XP over a short period of time to level up quickly, and so if you happen to have a spare Lucky Egg, you might want to hold back on evolving - saving those Pidgeys, Caterpies, and Weedles in particular.
Generally, you want to completely avoid evolving in the early game unless you're using that Lucky Egg strategy. You can't battle Gyms until Level 5, and can't reasonably get any Pokémon that could actually challenge a Gym until the Level 10-15 mark. As tempting as it can be to get that first one under your belt, because you'll likely catch stronger Pokémon as you Level up as a Trainer anyway, it really is best to wait.
A Pokémon's IVs - or natural strength or potential - stay the same after it has evolved.
A Pokémon's moves are randomised each time it evolves, and can't be changed in any other way.
You should always evolve a Pokémon fully when you can - so, a Geodude all the way through Graveler to a Golem - because otherwise the time it takes to earn another 100 Candy for your respective Pokémon will likely see you level up enough to catch a higher Level version. Waiting to do it in one go saves you the time and resources it would cost to Power Up a low-Level Pokémon to the same Level as one you've caught later on.
When is the best time to evolve and Power Up Pokemon?
We've decided to put together a flowchart, which should hopefully clear up what is a fairly complicated decision-making process for you! All the information you need is here - such as an IV calculator, CP and IVs explained, and a list of the best Pokémon in Pokémon Go - if you need it. Beneath the chart are the rules we've applied, but in text form.
You should Power Up your Pokémon if:
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You should evolve your Pokémon if:
You know it has strong IVs - because these won't change on evolution and
The Pokémon doesn't have very low CP - because if you're still a low-Level Trainer, you're likely to find an equally strong one when you have a higher Trainer Level down the line.
You should avoid Powering Up your Pokémon if:
It has average or low IVs - because these won't change on evolution
If it has yet to evolve - because evolving a Pokémon randomises it's moves, and could leave you with something awful.
It has very low CP, even if it still has strong IVs - because Powering Up can get very expensive very quickly, you're likely to find something already at a higher CP and equally as strong down the line, that will save you all that Stardust and Candy.
You should avoid evolving your Pokémon if:
It has low IVs and you care about its strength in battle.
It is fully evolved but has poor moves, regardless of IVs, and you care about its strength in battle.
It has very low CP, perhaps because you're still quite a low Trainer Level, regardless of its IVs - because you're likely to find Pokémon with as strong IVs but a higher CP down the line, saving you the cost of evolving it and then Powering Up to your level.
Essentially, the Power Up and evolving decisions that you make depend on what you want to achieve. For the collectors it's fairly simple - just evolve the Pokémon whose evolutions are particularly rare - but for those interested in getting the absolute most out of their Pokémon's battling capabilities, it's certainly less so.