Staring at your data, wondering: "What chart should I use?"
You're not alone. Choosing the wrong chart type is the #1 mistake in data visualization.
Use a pie chart when you need a bar chart? Your data looks confusing. Use a line chart for categories? Your audience is lost. Use the right chart? Your message is crystal clear.
In this guide, you'll learn exactly which chart to use for any data—with real examples, pro tips, and a simple decision flowchart.
Why Chart Type Matters
The Wrong Chart Costs You
Real example: A sales manager presented quarterly results with a pie chart showing sales trends over time. The CEO was confused. "Are sales going up or down?"
The problem: Pie charts show composition (parts of a whole), not trends over time. A line chart would have made the upward trend instantly clear.
The cost: 30 minutes of meeting time wasted explaining. Trust in the data team diminished.
The Right Chart Wins
Different scenario: Same data, line chart. CEO sees the upward trend in 3 seconds. "Great work! What's driving this growth?"
The result: Clear communication. Faster decisions. More trust.
The Rule
Your chart type must match your data structure and your message.
- Comparison? → Bar chart
- Trend over time? → Line chart
- Relationship? → Scatter plot
- Distribution? → Histogram
- Composition? → Pie chart
The 7 Essential Chart Types
These 7 charts handle 95% of data visualization needs. Master these, and you're set.
1. Bar Chart: Compare Values Across Categories
What it does: Shows which category is bigger/smaller
When to use:
- Comparing sales by product
- Survey results by category
- Performance by team/region
- Any "which is bigger?" question
Best practices:
- Start Y-axis at zero (don't cut off bars)
- Sort bars by value (highest to lowest)
- Use horizontal bars for long labels
- Limit to 15 categories maximum
Pro tip: Color the top performer differently to draw attention.
2. Line Chart: Show Trends Over Time
What it does: Reveals how something changes over time
When to use:
- Monthly sales over a year
- Website traffic over time
- Stock prices
- Temperature changes
Best practices:
- X-axis must be time (dates, months, years)
- Use multiple lines to compare (2023 vs 2024)
- Add data labels for key points
- Keep to 5 lines maximum
3. Pie Chart: Show Parts of a Whole
What it does: Displays proportions that add up to 100%
When to use:
- Market share breakdown
- Budget allocation
- Survey: "What's your favorite...?"
Best practices:
- Only 3-7 slices (more = unreadable)
- Start largest slice at 12 o'clock
- Label with percentages
- Use contrasting colors
When to skip pie charts: If you need precise comparisons, use a bar chart. Humans are bad at comparing angles but good at comparing bar lengths.
4. Scatter Plot: Reveal Relationships Between Variables
What it does: Shows if two numeric variables are related
When to use:
- Testing for correlation
- Finding patterns/clusters
- Identifying outliers
- Scientific data analysis
Pro tip: Add different colors for categories to reveal deeper patterns.
5. Histogram: Show Distribution of Data
What it does: Shows how values are spread across ranges
When to use:
- Age distribution in a population
- Test score ranges
- Income brackets
- Response times
Pro tip: Try different bin sizes. Too many bins = noisy. Too few = miss patterns.
6. Box Plot: Statistical Summary at a Glance
What it does: Shows median, quartiles, and outliers
When to use:
- Comparing distributions across groups
- Identifying outliers
- Academic/scientific contexts
Pro tip: Pair with histogram for full picture. Box plot shows summary, histogram shows shape.
7. Heatmap: Reveal Patterns with Color
What it does: Uses color intensity to show data values
When to use:
- Correlation matrices
- Time-based patterns (hour × day)
- Geographic data
- Website analytics (click patterns)
How to Choose: Decision Flowchart
Start Here: What's Your Question?
Question Type A: "Which is bigger?" → Bar Chart
Question Type B: "How has it changed over time?" → Line Chart
Question Type C: "Are these two things related?" → Scatter Plot
Question Type D: "How is the data distributed?" → Histogram or Box Plot
Question Type E: "What is it made of?" → Pie Chart
Question Type F: "What patterns exist across two dimensions?" → Heatmap
Quick Decision Matrix
| Your Data | Your Goal | Best Chart |
|---|---|---|
| Categories + Values | Compare | Bar Chart |
| Time + Values | Show trend | Line Chart |
| Number + Number | Find relationship | Scatter Plot |
| Single variable | Show distribution | Histogram |
| Categories + Values | Show composition | Pie Chart |
| Groups + Values | Statistical comparison | Box Plot |
| Two dimensions | Find patterns | Heatmap |
Common Mistakes to Avoid
Mistake #1: Using Pie Chart for Comparisons
Fix: Use pie charts ONLY for 3-7 categories showing composition.
Mistake #2: Line Chart for Categorical Data
Fix: Use bar chart for categorical comparisons.
Mistake #3: Bar Chart Starting Above Zero
Fix: Y-axis starts at zero for bar charts.
Mistake #4: Too Many Variables on One Chart
Fix: Show top 5, or create multiple charts.
Mistake #5: 3D Charts (Ever!)
Fix: Always use 2D. Always.
Chart Type Comparison Table
| Chart Type | Best For | Complexity |
|---|---|---|
| Bar Chart | Comparison | Simple |
| Line Chart | Trends | Simple |
| Pie Chart | Composition | Simple |
| Scatter Plot | Relationships | Moderate |
| Histogram | Distribution | Moderate |
| Box Plot | Statistical | Complex |
| Heatmap | Patterns | Moderate |
Frequently Asked Questions
Can I use multiple chart types for the same data?
Yes! Different charts reveal different insights. Use the chart that best answers your specific question.
How do I decide between bar chart and pie chart?
Use bar chart when: You have >7 categories, precise comparison matters, or values are close in size.
Use pie chart when: You have 3-7 categories and "part of whole" is the key message.
When in doubt: Bar chart is safer.
What's the most common chart type mistake?
Using the wrong chart type entirely. Fix: Ask "What's my ONE question?" and use the decision flowchart above.
Conclusion
You now know:
- The 7 essential chart types (covering 95% of needs)
- When to use each one (decision flowchart)
- How they work (with real examples)
- Common mistakes to avoid
The secret: Match your chart type to your question.
The result: Clear communication. Faster decisions. More trust in your data.