Question

In XY, Whats the percentage than a shiny will appear randomly?

Answer 1

The chance for a shiny Pokemon to appear randomly in X/Y and ORAS is 1/4096, or 0.02441%.
Having the Shiny Charm will triple this rate to 3/4096, or 0.07324%.

Source

Comments

i know it's easy to calculate from fraction... but OP did specify "percentage"