how to make a text inside a circle div fitting correctly, where div size is not fixed?

how to make a text inside a circle div fitting correctly, where div size
is not fixed?

I have circle div inside which i have a long text it is looking fine if
the circle div is big but when the size of the div is decreased the text
is overflowing. here is the fiddle
I want the text to fit inside this div.the div size is changeable so no
matter the div size but the text should fit accordingly. any help?
#ff{
width:80px;
height:80px;
background-color:red;
border-radius:100%;
position:absolute;
text-align:center;
line-height:80px;
}