What is the size of earth's crust?
Not 100% sure what you are referring to when you say "size" but I can say ~40% of Earths surface is covered by continental crust and the rest by oceanic crust. These combined make up the lithosphere (rigid part sitting on the mantle).
On average the continental crust is ~30km thick and in some places it can be less. It can also be thicker in other regions, usually mountainous regions where it can get up to about 60km thick.
The oceanic crust on the other hand is on average 8-10 km thick and has a more homogenous thickness than the continental crust.