.center { display: flex; justify-content: center; align-items: center; height: 200px; border: 3px solid green; }
button{ /*Change the width as much as you like, but make sure margin-left and margin-right + width = 100%*/ width:50%; margin-left:25%; margin-right:25%; }
<div style="text-align:center;"> <button>button1</button> <button>button2</button> </div>