Size encoding in Tableau - Step-by-Step Guide

Introduction

Size encoding changes the size of marks in your Tableau chart to show differences in data values. It helps you see which items are bigger or smaller at a glance, making comparisons easier.

When you want to show sales amounts by making bigger circles for higher sales.

When comparing the number of customers across different regions using different sized bars.

When highlighting the volume of products sold by changing the size of shapes on a map.

When you want to add a visual layer to a scatter plot to show a third measure by size.

When you need to emphasize important data points by making them larger.

Steps

Step 1: Open your Tableau workbook and select the worksheet with your chart

- Tableau workspace

Your chart is visible and ready for editing

Step 2: Drag the measure you want to use for size onto the Size button

- Marks card

The marks in your chart change size based on the measure values

💡 Use a measure with meaningful numeric values for size encoding

Step 3: Click the Size button on the Marks card

- Marks card

A slider appears allowing you to adjust the size range of marks

Step 4: Drag the slider to increase or decrease mark sizes

- Size slider on Marks card

Marks become larger or smaller, making differences clearer

Step 5: Observe the chart to ensure size differences are visible and meaningful

- Tableau worksheet

You can easily compare data points by their size

Before vs After

Before

All marks in the chart are the same size, making it hard to see differences in values

After

Marks vary in size according to the measure, so larger values have bigger marks and smaller values have smaller marks

Settings Reference

Size slider

📍 Marks card > Size

Control the minimum and maximum size of marks for better visibility

Default: Medium size range

Measure for size

📍 Data pane > Drag measure to Size on Marks card

Determines how mark sizes vary based on data values

Default: None

Common Mistakes

Using a dimension instead of a measure for size encoding

Dimensions are categories and do not have numeric values to scale sizes properly

Always use a numeric measure to control mark size for meaningful visual differences

Setting the size slider too small or too large

Marks become too tiny to see or too big and overlap, making the chart confusing

Adjust the size slider to a balanced range where size differences are clear but marks do not overlap excessively

Summary

Size encoding changes mark sizes to represent numeric data values visually.

Use numeric measures for size to show meaningful differences.

Adjust the size slider to make marks clear and easy to compare.

Practice

1. What is the main purpose of size encoding in Tableau visualizations?

easy

A. To sort data in ascending or descending order

B. To change the color of marks based on categories

C. To filter data points from the view

D. To change the size of marks based on data values

Solution

1. Step 1: Understand size encoding concept

   Size encoding adjusts the size of visual marks to represent numeric data values visually.

2. Step 2: Compare options with concept

   Only To change the size of marks based on data values describes changing mark size based on data values, which matches size encoding.

3. Final Answer:

   To change the size of marks based on data values -> Option D

4. Quick Check:

   Size encoding = mark size by data [OK]

Hint: Size encoding changes mark size to show data amounts [OK]

Common Mistakes:

• Confusing size encoding with color encoding
• Thinking size encoding filters data
• Assuming size encoding sorts data

2. Which of the following is the correct way to apply size encoding in Tableau?

easy

A. Drag a measure field to the Color shelf

B. Drag a dimension field to the Size shelf

C. Drag a measure field to the Size shelf

D. Drag a dimension field to the Filters shelf

Solution

1. Step 1: Identify what type of field size encoding uses

   Size encoding requires numeric data, so it uses measure fields.

2. Step 2: Match correct shelf for size encoding

   Size shelf controls mark size, so dragging a measure field there is correct.

3. Final Answer:

   Drag a measure field to the Size shelf -> Option C

4. Quick Check:

   Size shelf + measure field = correct size encoding [OK]

Hint: Size encoding needs numeric (measure) fields on Size shelf [OK]

Common Mistakes:

• Using dimension fields instead of measures
• Dragging fields to Color shelf instead of Size
• Confusing Filters shelf with Size shelf

3. Given a bar chart with sales amounts encoded by size, what happens if you increase the size range in Tableau's Size legend?

medium

A. Bars with higher sales become noticeably larger compared to smaller sales bars

B. All bars become uniformly larger regardless of sales

C. Bars change color instead of size

D. The chart filters out smaller sales bars

Solution

1. Step 1: Understand effect of increasing size range

   Increasing size range makes size differences more pronounced between small and large values.

2. Step 2: Analyze impact on bars

   Bars with higher sales grow larger relative to smaller sales bars, enhancing visual comparison.

3. Final Answer:

   Bars with higher sales become noticeably larger compared to smaller sales bars -> Option A

4. Quick Check:

   Increase size range = bigger size difference [OK]

Hint: Larger size range exaggerates size differences [OK]

Common Mistakes:

• Thinking all bars grow equally
• Confusing size changes with color changes
• Assuming filtering happens automatically

4. You applied size encoding to a measure but notice all marks are the same size. What is the most likely cause?

medium

A. The measure has the same value for all data points

B. You dragged a dimension field to the Size shelf

C. The color legend is overriding size encoding

D. The data source is disconnected

Solution

1. Step 1: Check measure values for size encoding

   If all measure values are identical, size encoding cannot differentiate mark sizes.

2. Step 2: Evaluate other options

   Dragging dimension to Size shelf would cause error, color legend does not override size, and disconnected data prevents any marks.

3. Final Answer:

   The measure has the same value for all data points -> Option A

4. Quick Check:

   Same measure values = same mark size [OK]

Hint: Check if measure values vary to see size differences [OK]

Common Mistakes:

• Assuming dimension fields work for size encoding
• Thinking color affects size encoding directly
• Ignoring data connection status

5. You want to create a scatter plot where the size of each point shows the total sales per region, but some points appear too small to see. What is the best way to improve size encoding clarity?

hard

A. Remove size encoding and use color encoding instead

B. Increase the maximum size in the Size legend and use a logarithmic scale for sales

C. Filter out regions with small sales values

D. Use a dimension field on the Size shelf instead of sales

Solution

1. Step 1: Address small point visibility

   Increasing maximum size makes larger points bigger and more visible.

2. Step 2: Use logarithmic scale for better size distribution

   Log scale reduces skew from very large sales, improving size differences for smaller points.

3. Final Answer:

   Increase the maximum size in the Size legend and use a logarithmic scale for sales -> Option B

4. Quick Check:

   Max size + log scale = clearer size differences [OK]

Hint: Use max size and log scale to fix tiny marks [OK]

Common Mistakes:

• Removing size encoding loses visual comparison
• Filtering data hides information unnecessarily
• Using dimension fields for size causes errors