Like most things Pokemon Go related, the community has come through and delivered more information than the developer has given.
This new tidbit comes by way of GameSpot, who provided the exact mileage (kilometers, actually) needed to earn enough candies to evolve every creature with the buddy system. The most interesting bit on the chart? Magikarp, who requires 400 candies to evolve into Gyrados, will earn one candy per kilometer — that’s 248.5 miles in all with Magikarp as your buddy.
But that one absurd example aside, I like the idea for leveling purposes especially. If you’re trying to walk 30-40 miles to evolve something it’s going to be tedious, but you’ll naturally earn enough candy to boost the stats of several of your party members with each level — especially late game.