This snippet let you create a circle box without knowing the width and the height, so the circle will be responsive with the container.
<div class="circle">
<span>
-- CONTENT --
</span>
</div>
.circle {
display: inline-block;
border-radius: 50%;
min-width: 20px;
min-height: 20px;
padding: 5px;
background: #2c93b1;
color: white;
text-align: center;
line-height: 1;
box-sizing: content-box;
white-space: nowrap;
width: 100%;
&:before {
content: "";
display: inline-block;
vertical-align: middle;
padding-top: 100%;
height: 0;
}
span {
display: inline-block;
vertical-align: middle;
}
}