Comment by Thorrez

The birthday paradox equation is approximately the square root. You expect to find a collision in 365 possibilities in ~sqrt(365) = ~19 tries.

You expect to find a collision in 2^256 possibilities in ~sqrt(2^256) = ~2^128 tries.

You expect to find a collision in 10^10000 possibilities in ~sqrt(10^10000) = ~10^5000 tries.