Circle button css

Question

I\'m a beginner and very confused, as a div tag when I give the same width and height with border-radius: 50% it always becomes circle. but with the tag a in case I want to

Answer 1

.round-button {
  width:25%;
}
.round-button-circle {
  width: 100%;
  height:0;
  padding-bottom: 100%;
  border-radius: 50%;
  border:10px solid #cfdcec;
  overflow:hidden;
        
  background: #4679BD; 
  box-shadow: 0 0 3px gray;
}
.round-button-circle:hover {
  background:#30588e;
}
.round-button a {
  display:block;
  float:left;
  width:100%;
  padding-top:50%;
  padding-bottom:50%;
  line-height:1em;
  margin-top:-0.5em;
        
  text-align:center;
  color:#e2eaf3;
  font-family:Verdana;
  font-size:1.2em;
  font-weight:bold;
  text-decoration:none;
}

Button!!

or very simple for

.round-button {
    display:block;
    width:80px;
    height:80px;
    line-height:80px;
    border: 2px solid #f5f5f5;
    border-radius: 50%;
    color:#f5f5f5;
    text-align:center;
    text-decoration:none;
    background: #555777;
    box-shadow: 0 0 3px gray;
    font-size:20px;
    font-weight:bold;
}
.round-button:hover {
    background: #777555;
}

Button

for jsfiddle reference click here