如何让同一页面中的多个ChartJS图表保持相同高度与均等柱宽？

Hey everyone, I wanted to share a frustrating little behavior I ran into recently when working with multiple vertical bar charts on the same page:

When you have multiple bar charts where each has a different number of columns (dataset size), even if you try to make them look identical, the column widths will end up inconsistent.

Why does this happen? #

Most popular charting libraries (think Chart.js, Highcharts, etc.) calculate bar widths automatically by default based on two key factors:

• The total width of the chart container
• The number of data categories (columns) in the dataset

So if one chart has 5 columns and another has 10, the library will shrink the 10-column chart's bars to fit all of them into the same container width. That means narrower bars compared to the 5-column one—even if you’ve set the same overall styling rules.

How to fix it? #

The exact fix depends on the library you’re using, but here are some reliable approaches:

• Set a fixed bar width: Look for config options that let you lock in an explicit bar size. For example, in Chart.js, you can use barPercentage and categoryPercentage together to maintain consistent width, or use barThickness for a fixed pixel value:

  // Example with Chart.js
  options: {
    scales: {
      x: {
        barPercentage: 0.6,
        categoryPercentage: 0.8
      }
    }
  }
  

• Standardize spacing: Instead of relying on auto-calculated gaps, set fixed padding between bars and between the chart edges and the first/last bar. This ensures the space allocated for bars stays consistent no matter how many columns you have.
• Adjust container widths dynamically: If fixed bar widths aren’t feasible, calculate and set different container widths based on the number of columns—this way, bar width stays uniform across all charts.

It’s a small gotcha, but once you know what’s causing it, fixing it is pretty straightforward!

内容的提问来源于stack exchange，提问作者Zsolt Kálmán