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.