.piechart {
    position: relative;
    display: inline-block;
    text-align: center;
}
.piechart span{
    position: absolute;
    left: 0;
    right: 0;
    top: 40%;
    z-index: 2;
}
.piechart span:after {
    content: '%';
    margin-left: 0.1em;
    font-size: .8em;
}
.piechart canvas {
    position: relative;
    top: 0;
    left: 0;
}