What is a Bullet Chart?
A simple data visualization based on the bar chart, the bullet chart features a single quantitative measure, along with a few secondary measures, and displays progress toward a certain target or goal. A bullet chart takes the shape of a rectangle with distinct sections, focusing on a centered bar that shows the quantitative measure. This chart can be either horizontal or vertical, depending on the available space for the visualization. The structure consists of four important components as shown in the visual below:
- Featured Measure: The center bar of the rectangle that displays the primary performance measure.
- Comparative Measure: The measure or measures against which you want to compare your featured measure; the target or goal value, often indicated by a line perpendicular to the orientation of the chart.
- Quantitative Scale: Measures the numerical value of the featured and comparative measures on a linear axis.
- Qualitative Scale: The background shade intensity of the chart that indicates different qualitative ranges like bad, satisfactory, and good; optional component.
When to Use a Bullet Chart
As mentioned above, bullet charts should be used when wanting to compare a current value to a specified set goal value. While this comparison is the main focus of a bullet chart, it can also be used to show important milestones in progress to the future goal. The quantitative scale along with extra marking lines make it obvious when important milestones are met, like being 50% or 75% of the way to reaching the set goal. With this being said, bullet charts can only be used if a reasonable, attainable, and specific goal is set.
Because bullet charts can have an optional qualitative scale, they can be used to explain progress toward a goal in a simple way that anyone can understand. The qualitative scale breaks the quantitative scale into ranges and gives them a label that describes a state like poor, satisfactory, and excellent. Without even having to look at the quantitative scale, it’s easy to see how goal progression is coming along in a more general sense. Though the qualitative scale isn’t necessary, bullet charts with one should be able to be split into at least two ranges.
Let’s take a look at an example where the bullet chart is a great choice of visualization:
In this example, we’re interested in looking at a business’s yearly revenue as of the month of June. The blue bar represents the current revenue value (the featured measure), the black line represents the goal revenue value (the comparative measure), the numbers represent the quantitative scale, and the three different shaded regions represent the qualitative scale. Note that there isn’t a chart legend to explain the significance of the shading for the qualitative scale– in most bullet charts, including this one, darker shading indicates poorer performance and lighter shading indicates better performance.
From the bullet chart, it’s easy to see that the business’s current revenue value is around 1.5 million dollars and that the business’s goal revenue is around 2.5 million dollars. Their current revenue has surpassed the poor performance zone, below 1 million dollars, and is currently in the middle of the satisfactory performance zone, above 1 million and below 2 million dollars. Since the current revenue value is for the month of June, we’re able to conclude from the chart that the business has approximately six months to increase their revenue 1 million dollars to reach their set goal for the year.
When NOT to Use a Bullet Chart
Determining when to use a bullet chart is usually simple, but there are some areas where a bullet chart is not the ideal visualization choice. First, bullet charts should not be used when there are a large number of ranges on the qualitative scale. With too many ranges, shading becomes hard to distinguish and distracts from the featured measure in the center of the chart.
Second, bullet charts aren’t an ideal chart type when the featured measure value is significantly less than the comparative measure value or values that define the ranges for the qualitative scale. This skews the overall distribution of the chart and makes the value of the featured measure difficult to interpret, unless a detailed quantitative scale is provided. The skewness, however, isn’t an issue if the goal of the chart is to show the featured measure’s qualitative standing instead of its quantitative value. Let’s look at an example of this:
This example is very similar to the previous one– we’re still interested in looking at a business’s yearly revenue as of the month of June. The blue bar still represents the current revenue value (the featured measure), the black line still represents the goal revenue value (the comparative measure), the numbers still represent the quantitative scale, and the three different shaded regions still represent the qualitative scale. The significance of the shading is also the same as in the previous example: darker shading indicates poorer performance and lighter shading indicates better performance.
So why is the bullet chart a poor choice of visualization for this data? Well, it’s obvious that the chart is skewed to the right, making it very difficult to interpret the numerical value of the featured measure; the comparative measure and values defining the qualitative scale are too large compared to the featured measure.
From the chart we can still see that the business’s current revenue is in the poor performance zone and that there’s a long way to the goal revenue. However, we can’t tell what the current value or the goal value is, or exactly how much the revenue needs to increase in six months to reach the business’s goal for the year. Depending on the goal for the visualization, this chart either works or it doesn’t.
Comparison of Single Value Chart Types
Simply put, the bullet chart is a data visualization that depicts a single value in relation to a set goal. Other types of visualizations that show individual values are the single value chart and single value indicator chart. The table below gives the use case and pros and cons of the bullet, single value, and single value indicator charts:
Single Value Chart
Single Value Indicator Chart