Designing Charts: Axis Tick Marks

Choosing the right number of axis tick marks is important for creating clear and effective data visualizations. Here are some simple guidelines to help you choose the appropriate number of ticks for your visuals:

  • Consider the scale and size of your chart: The first thing to think about is how large your chart will be on the page or screen. If you have a small chart, including too many tick marks might not be practical, as they can become cluttered and hard to read. On the flip side, if you have a large chart, you might need more tick marks to effectively represent the data. 
  • Think about the data range: The range of your data will also influence the number of tick marks needed. Fewer tick marks might be necessary if you’re working with a small data range.
  • Use meaningful intervals: The tick marks should correspond to meaningful intervals in your data. For example, if you’re charting the total number of monthly sales, using 10, 20, or 50 intervals might make sense as they are more comprehensible to readers. If you’re plotting historical financial data, like a company’s revenue, using major intervals like 100, 1000, 10000, or higher might be necessary to appropriately show revenue trends.
  • Keep it simple: As a general rule of thumb, aim for simplicity when choosing the number of tick marks. Too many tick marks could lead to visual clutter and make the chart difficult to read, while too few can make it hard for your audience to understand the data. A good starting point is to have around 5-7 tick marks on each axis, adjusting as needed based on the scale of your chart and data range.
  • Test and refine: As you create your visual, don’t be afraid to test and refine the number of tick marks until you find the right balance for your chart. 

  Types of tick marks to consider:

  • Continuous tick marks are used when representing numerical data on an axis with a continuous range. They provide reference points at regular intervals along the axis to indicate specific numerical values. The spacing between the tick marks is usually determined based on the scale and range of the data.
  • Discrete tick marks on a chart refer to a specific type of tick marks that are used when the data being represented on the axis is categorical or qualitative in nature. Unlike continuous tick marks, which represent a numerical range, discrete tick marks are used to indicate specific categories or distinct data points along the axis.
  • Logarithmic tick marks are used when the data being represented spans a wide range of values that vary exponentially. Instead of using linear intervals, logarithmic tick marks are spaced at exponential intervals (e.g., powers of 10) to accommodate the exponential nature of the data.
  • Minor tick marks are smaller tick marks placed between major tick marks to provide additional reference points and improve the granularity of the axis. They are used to represent intermediate values or subintervals between major intervals and assist in interpreting the data with greater precision.
  • Data-driven tick marks are tick marks that can be customized or adjusted based on the specific data being represented. For example, if the data has notable outliers or important threshold values, custom tick marks can be added to highlight those specific points of interest. These data-driven tick marks help draw attention to critical data features.
  • Labeled tick marks: Tick marks are often accompanied by labels that indicate the corresponding values or categories. Labeled tick marks provide clear identification and help users understand the scale or meaning of the data points along the axis. The labels can be numeric values, categorical labels, or any other relevant information.
  • Dual-axis tick marks: In charts with dual axes, where two different data sets or scales are represented on separate axes, tick marks are used on each axis to indicate the respective values. Dual-axis tick marks ensure that viewers can associate the correct values with the corresponding data set.