website design – How to adjust button dimensions to be equal and equally responsive

I have four buttons, and because the overlaying is of different lengths, the buttons have different dimensions. What CSS do I add to make all buttons have the same dimensions regardless of text length (see attached images)? I have tried combinations of padding (I think it is about adding padding to the smaller buttons to match the largest button, yes?) without any success.
Image: Buttons and CSSenter image description here