What is the maximum number of Pokemon I can hold in my box Let's Go Pikachu/Eevee?

Question

I'd just like to know how many I can capture before needing to transfer some to the professor.

Answer 1

The total number of Pokémon you can keep is 1,000, an increase from the 960 Pokémon trainers could have in Pokémon Ultra Sun and Pokémon Ultra Moon.

Source