What is the formula to calculate the shiny encounter rate in hordes?

Question

Finding a shiny Pokemon chance is 1/8192 but it's been reduced to 1/4096.
I don't know what the shiny encounter rate is and how would I calculate the rate withthe shiny ccharm?

Answer 1

The shiny charm changes the rate of getting a shiny by +2/8192 in Gen5 and 2/4096 in Gen 6.
And the formula for horde shininess is just the shiny chance multiplied by 5.
For each individual Pokemon with a shiny charm, this would be a 3/4096 chance.

5(3/4096) = 15/4096
Or, with a numerator of one, 1/273.0666666666...

Source of Formulas and shiny charm increase: Guy in the comments

Comments

Are you sure? Wouldn't the shiny charm increase the odds for each individual Pokemon?
5(1/4096) + 5(2/4096) = 5(3/4096) = 15/4096 = 1/273 chance per battle
I hardly run into hordes, so I wouldn't really know, but this seems more logical to me. Unless you can list an actual source, there is nothing to say that your answer is correct.

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Yes. Yes it would.

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Well you can change your source from "Experience" to "Guy in the comments" now :)