[Chartjs]-Can't set ChartJS canvas width

You should be able to disable this container-width filling behaviour by telling Chart.js not to use responsive mode. Try passing this into the global configuration of the chart (the highest level of options):

options: {
    responsive: false
}

See the Chart.js documentation for an example of how this fits into the full definition of a chart.

If that does not work for some reason then you could instead limit the width of the div element which contains the canvas on which your graph is drawn. Based on your example you could add this to your CSS:

div#pnlChart {width: 200px}

Even if you can get one of these methods to work, ideally you don’t want to be specifying fixed widths for items these days because it makes it harder for pages to display well on the myriad of device screens which are in use now.

It’s much better to develop a responsive layout for your site which will adjust to suit any screen width, from small smartphones to large desktop monitors. Search online for guides about “responsive design” for articles about this subject.