What is the average stat change after Pokemon Evolution?

There's a pokemon I think should evolve, so I'm making my own fake one, and I'm doing everything about it, like base stats and move pool and all.

So what I want to know is how much does each base stat change after a pokemon evolves.

For example, Bulbasaur has base stats of 45 49 49 65 65 45. Ivysaur's base stats are 60 62 63 80 80 60 and the differnces are 15 14 15 15 15 15. What I want to know is the average change across all Pokemon using this method of calculation.

3 Answers

I gathered the information on pokemon stats and evolution lines from bulbapedia (Up to gen VI, or #721), and threw it all into a spreadsheet to do some calculations.

Here is the relevant table of stat changes when evolving. Results are rounded to nearest integer.

Note that your desired values for all evolutions are

25 28 23 27 25 20

Mega evolutions were not included, and they will always increase the base stat total by 100 (but individual stats could decrease).

As a side note, a new (non-mega) evolution should probably have no more than 600 total stats, as this is the value for "pseudo-legendaries", which are the typical peak for non-legendary pokemon.

Sources:

1 - Pokemon Stats

2 - Evolution Lines

3 - Pseudo-Legendaries

I can't tell you the average stats per evolution, but here's the average stats for all pokemon and fully evolved pokemon:

Attack
The average Attack stat is 75 for all Pokémon, and the average for all fully evolved Pokémon is 90.
Defense
The average Defense stat is 70 for all Pokémon, and the average for all fully evolved Pokémon is 83.
Special Attack
The average Special Attack Stat is 69 for all Pokémon, and the average for all fully evolved Pokémon is 83.
Special Defense
The average Special Defense stat is 69 for all Pokémon, and the average for all fully evolved Pokémon is 83.
Speed
The average Speed stat is 66 for all Pokémon, and the average for all fully evolved Pokémon is 78.

Source

I don't think your current approach will get you what you want. Using an average on all evolved Pokemon will get you...well, an average evolved Pokemon. Evolution can entirely change the way a monster is used. I would recommend using the information from Pokemon builds that fall within a single class and possibly further narrow your numbers to a particular tier. Also, you may want to keep in mind that stats aren't the only thing that determine the usability of a monster. In case you don't know about classes and/or tiers, I'll include some more info below:

Classes

Pokemon "builds" can be grouped according to their function in battle (sweepers, walls, annoyers, healers, etc.). The following all work together to determine the class of a given monster:

• stats*
• ability*
• move pool
• typing*
• item

*These can change after mega evolution or because of other items like: Eviolite, Light Ball, Choice items, etc. (Stats can also change based on breeding and nurturing, but the details are too much for this answer.)

Tiers

Competitive battling communities (such as Smogon) have grouped Pokemon into Tiers depending on their usage for each generation. These are commonly seen as Uber, BL, OU, UU and NU. You could possibly use these groupings alongside the class to better focus your numbers/builds.