knowing running time from given algorithm complexity

Hi guys, let's say we know our algorithm complexity, so we know how many operations(give or take) our program will do, but how to know if it will stand in the time limits?

Let's say we algorithm with complexity of N*sqrt(N), and N = 10^5, will this algorithm finish in 1 second?

For purpose of this question let's assume we are using c++.

Thanks!