There are so many hidden mechanics to Pokemon GO (Free) that it can get pretty overwhelming at times. Each Pokemon has a hidden stat for Attack, Defense and Stamina that is unique to each specific creature of its species, and so while my Rattata may be in the top percentage of Rattatas, yours may be pitifully weak in comparison. These secret stats are intrinsic to the amount of CP of the specific Pokemon, and therefore are vitally important in how many bonus Combat Points they may receive when evolving. As candies are such a rare commodity for some evolutionary lines, and a lot of the time it seems like a shot in the dark to how much a Pokemon will grow when it evolves, Reddit user Kyurun has compiled a list, which I have turned into a beautiful table, stating the minimum CP requirement for any Pokemon to end up breaking the 1000CP threshold when it eventually evolves into its final form.
While Kyurun stresses that the website may not be 100% accurate so treat the results with caution, it is also worth noting that the CP figures are the absolute minimum needed to get your Combat Points over one thousand after evolving. This is because each Pokemon has a multiplier that is dependent on the hidden stats, which can be calculated at the PokeAssistant website; the figures compiled in the Reddit post are using the lower bound multiplier for the weakest possible Pokemon, and so there is a chance that weaker Pokemon could break the 1000CP barrier if they have commendable hidden stats, and therefore a higher multiplier. Despite this, if you are curious about the potential of your beloved Metapod, be sure to use the Pokemon GO Toolkit website to discover the potential of your specific Pokemon through its CP. Hopefully in future updates Niantic will begin to make some of these Pokemon GO mechanics clearer, or at least more visible. But please fix the tracker first.