CSS circle without using fixed width and height - html

Question

I want to display the notification count inside a circle but I don't want it to have a fixed width so the circle can expand when there is a bigger number/text inside the circle.
.circle {
height: 20px;
width: 20px;
line-height: 20px;
border-radius: 50%;
background-color: red;
color: white;
text-align: center;
}
<div class="circle">5</div>
<br>
<div class="circle">102</div>

Answer 1

See this CSS only solution. Set the same value of min-width and min-height for 1 digit number. Use a pseudo element for vertical alignment and to maintain the square shape. With border-radius applies to the container for the circle.
.circle {
display: inline-block;
border-radius: 50%;
min-width: 20px;
min-height: 20px;
padding: 5px;
background: red;
color: white;
text-align: center;
line-height: 1;
box-sizing: content-box;
white-space: nowrap;
}
.circle:before {
content: "";
display: inline-block;
vertical-align: middle;
padding-top: 100%;
height: 0;
}
.circle span {
display: inline-block;
vertical-align: middle;
}
<div class="circle"><span>8</span></div>
<div class="circle"><span>64</span></div>
<div class="circle"><span>512</span></div>
<div class="circle"><span>4096</span></div>

Answer 2

This is so hacky, but it seems to check out on all the major browsers' latest versions, so I'll post it anyway. The basic principle is that percent-based padding (even top and bottom padding) are relative to the width of the parent. Setting it to 100% with a width and height of 0 would theoretically mean that the height of the element would always be equal to the width. Combine that with a pseudo element and you don't even need to change the markup. I used flexbox to correct the centering of the content. It seems to work on the browsers I tested it on, but this is definitely dependent on recent versions because it uses flexbox and display:table. I also had to add a min-width to ensure it doesn't appear out of shape for too little of content.
.circle {
background-color: red;
color: white;
text-align: center;
position: relative;
border-radius: 50%;
min-width: 1.25em;
display: inline-flex;
align-items: center;
justify-content: center;
}
.circle:after {
content: '';
padding-top: 100%;
display:table;
}
<div class="circle">5</div>
<br>
<div class="circle">102</div>
<br>
<div class="circle">4298347918</div>

Answer 3

Simple CSS for circles that works almost ever:
.circle {
position: relative;
border-radius: 50%;
width: 100%;
height: auto;
padding-top: 100%;
}
The trick is that the padding top is calculated on the width so you can use it for makinh height equals width

Answer 4

Try using border-radius:50% and set max-width and height

Answer 5

Here is a quick example where you can see how to dynamically maintain a circle with css and js.
As Jagjit Singh pointed out here, you can achieve a circle using border-radius: 50%; instead of a fixed-pixel value.