Where can I find the rarity of a Pokemon?

I’m working on a project to create a simple Pokemon emerald clone, and now want to know the formula for a random encounter in tall grass. I found this:

“the formula should be:1 in (187.5 / ( x )) per stepLet x equal the a value which determines how rare the Pokémon is. The higher the encounter rate, the more common the Pokémon is.”

Does anyone know a place where I can find the rarity of each Pokemon? Preferably in JSON but anything is fine.

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There are many great websites out there,Pokémon Databaseincluded, that show you the rarity of the Pokémon found in the route, and even in certain parts out the route. Other great sites areSerebiiandBulbapedia.Mostof this is correct. To extract this, simply type in the route, then it will show you items, trainers, and the Pokémon found in the route. It will most likely be separated into grass, water, fishing rods, and talk grass, depending on the route. Next to each Pokémon will be a percentage, which represents the probability that you will encounter that Pokémon in any wild battle in that terrain. For example, if a Magicarp has a 90% next to it under old rod, you have a 90% chance (0.9, 9/10) of finding that Pokémon in any wild encounter. In a perfect world, all the percentages will add to 100%, so you will plug in the percents for x for each Pokémon in each terrain type.