[Solved]-How to set highchart boxplot size-Highcharts

use maxpointwidth or pointwidth option to control the box plot width.

highcharts.chart('container', {
  series: [{
    type: 'boxplot',
    maxpointwidth: 50,
    data: [
      [760, 801, 848, 895, 965]
    ]
  }]
});

demo:

https://jsfiddle.net/blacklabel/w86xv14d/

api reference:

https://api.highcharts.com/highcharts/series.boxplot.maxpointwidth https://api.highcharts.com/highcharts/series.boxplot.pointwidth