Setting width and height

I cannot believe nobody talked about using a relative parent element.

Code:

<div class="chart-container" style="position: relative; height:40vh; width:80vw">
  <canvas id="chart"></canvas>
</div>

Sources: Official documentation

You can also simply surround the chart with container (according to official doc http://www.chartjs.org/docs/latest/general/responsive.html#important-note)

<div class="chart-container">
    <canvas id="myCanvas"></canvas>
</div>

CSS

.chart-container {
    width: 1000px;
    height:600px
}

and with options

responsive:true
maintainAspectRatio: false

You can override the canvas style width !important ...

canvas{

  width:1000px !important;
  height:600px !important;

}

also

specify responsive:true, property under options..

options: {
    responsive: true,
    maintainAspectRatio: false,
    scales: {
        yAxes: [{
            ticks: {
                beginAtZero:true
            }
        }]
    }
}

update under options added : maintainAspectRatio: false,

link : http://codepen.io/theConstructor/pen/KMpqvo

In my case, passing responsive: false under options solved the problem. I'm not sure why everybody is telling you to do the opposite, especially since true is the default.