Power Up calculates stardust and candy needed to reach a target level. Evolve calculates how many Pokemon you can evolve from your current candy stock.
The Pokemon's current level. Half-levels (e.g. 20.5) are valid.
The level you want to reach. Levels above 40 require XL Candy and are gated by your trainer level.
Lucky Pokemon cost 50% less stardust. Shadow Pokemon cost 1.2x more candy and stardust. Purified Pokemon cost 10% less of both.