R2 and adjusted R2

Hello everybody,
I have just a quick question please. When we have only one IV, do we need to calculate adjusted R2, or R square is enough to know how well X explains Y. I am asking because as far as I know, R 2 increases everytime we add a variable, but if we only have one, R2 does not represent anymore the risk to be significant due to the number of variables... Right?


Fortran must die
Adjusted R square matters when comparing models with different number of variables. I am not sure why you would use it with one model.