Accepted answer

If you want to add %after the values of the Y-Axis you can do it using scales in your chart configuration. Your code will look like this:

var myBarChart = new Chart($("#myCanvas"), {
    type: 'bar',
    data: data,
    maintainAspectRatio: false,
    options: {
        scales: {
            yAxes: [{
                ticks: {
                    // Create scientific notation labels
                    callback: function(value, index, values) {
                        return value + ' %';

Documentation about scales

Fiddle updated with the %: Fiddle

And if you want to modify the text displayed in the tooltips you can easily change it using callback. You can find more information here Tooltip Callbacks

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