hi, you can do changes the radius of doughnut chart in chart.js in the line below :
var
Doughnut = function(data, config, ctx) {
var segmentTotal = 0;
var doughnutRadius = Min([height / 2, width / 2]) - 5;
var cutoutRadius = doughnutRadius * (config.percentageInnerCutout / 100);
for (var i = 0; i < data.length; i++) {
segmentTotal += data[i].value;
}
.....
regards