How to Label a Pie Chart

Proper labeling is the difference between a pie chart that communicates instantly and one that confuses your audience. Labels are your chart's voice—they tell viewers what they're looking at, how much each slice represents, and why it matters. This guide covers everything you need to know about pie chart labeling, from choosing between percentages and values to ensuring your labels are accessible to all users.

Percentages vs. Values vs. Names: Choosing the Right Label Type

The first decision you'll make is what information your labels should display. There are four common approaches, each with distinct use cases:

Percentage Labels

Best for: Showing proportions and relative comparisons when the total isn't critical.

Percentage labels answer the question "what share?" at a glance. Use them when your audience cares more about relative size than absolute numbers—for example, market share breakdowns, survey results, or budget allocation by category.

Value Labels

Best for: Financial data, counts, and cases where absolute numbers matter.

Value labels show the raw data. Use them when your audience needs to know the actual quantities—revenue figures, population counts, or unit sales. They're especially important in business presentations where stakeholders want concrete numbers, not just proportions.

Name Labels

Best for: Simple charts with distinct colors and a legend, or when space is limited.

Sometimes the category names alone are enough, especially when combined with a legend that shows the breakdown. This approach works best with 3-5 slices where the visual proportions tell most of the story.

Combination Labels (Name + Percentage)

Best for: General-purpose charts that need to be self-explanatory.

This is the most common approach and the safest choice when you're unsure. Combining the category name with its percentage gives viewers complete context without requiring them to reference a legend or do mental math.

Font Size and Readability

Your labels need to be legible at the size your chart will be viewed. Here are the rules of thumb:

• Minimum 10-12px for digital displays — Anything smaller becomes difficult to read on screens
• 14-16px for presentations — Viewers in the back of the room need larger text
• Scale proportionally — If you resize your chart, resize the labels too
• Use weight for hierarchy — Bold numbers with regular text for labels creates visual structure

Label Placement: Inside, Outside, or Callout Lines

Where you position labels dramatically affects readability. Each placement strategy has tradeoffs:

Inside the Slices

Pros: Clean, compact, makes efficient use of space.
Cons: Only works for slices larger than ~10%, requires sufficient color contrast.
Use when: You have 3-6 large slices with distinct colors.

Outside with Callout Lines

Pros: Works for any slice size, no contrast concerns, allows longer labels.
Cons: Takes more space, can look cluttered with many slices.
Use when: You have small slices or need detailed labels.

Using a Legend

Pros: Keeps the chart clean, works for many categories.
Cons: Requires viewers to match colors, adds cognitive load.
Use when: Space is extremely limited or you're showing the same categories across multiple charts.

Accessibility: Contrast and Screen Readers

Accessible labels ensure everyone can read your chart, including users with visual impairments or color blindness.

Color Contrast

Follow WCAG 2.1 guidelines: labels should have a contrast ratio of at least 4.5:1 against their background. Dark labels on light slices, light labels on dark slices. Avoid placing colored text on similarly colored backgrounds.

Screen Reader Support

When exporting as SVG for web use, add ARIA labels and title elements:

• Include a <title> element describing the chart's purpose
• Add role="img" and aria-label to the SVG element
• Consider providing a text alternative (table or list) alongside the chart

When to Use Legends vs. Direct Labels

Legends have their place, but direct labeling is almost always better for pie charts. Here's when to choose each:

Use direct labels when:

• You have 6 or fewer slices
• The chart will be viewed quickly (dashboards, social media)
• You want instant comprehension without eye movement between legend and chart

Use a legend when:

• You have many small slices where labels would overlap
• You're showing multiple related charts with the same categories (consistency matters)
• Space is extremely constrained
• You're using patterns or textures in addition to colors

In most cases, direct labels reduce cognitive load and make your chart easier to understand. Reserve legends for situations where labeling every slice would create clutter.