Pie Chart

A warning about pie charts

Pie charts are often hard to compare precisely.

Prefer:

Bar charts (best)
Donut charts only for simple cases

Still, you may see pie charts in reporting, so here’s how to make one safely.

diagram How a pie chart is built mermaid

  flowchart LR
  A["Category values"] --> B["Sum to get the total"]
  B --> C["Each value's share = value / total"]
  C --> D["Share * 360deg = slice angle"]
  D --> E["Slices drawn around a full circle"]

Each category's share of the total becomes an angle; all the angles together sweep a full circle.

Basic pie chart

Pie

import matplotlib.pyplot as plt
 
labels = ["A", "B", "C"]
values = [50, 30, 20]
 
plt.figure(figsize=(6, 6))
plt.pie(values, labels=labels, autopct="%1.0f%%", startangle=90)
plt.title("Category share")
plt.tight_layout()
plt.show()

Improve readability

Explode biggest slice

import matplotlib.pyplot as plt
 
explode = [0.1, 0.0, 0.0]
 
plt.figure(figsize=(6, 6))
plt.pie(values, labels=labels, autopct="%1.0f%%", startangle=90, explode=explode)
plt.title("Category share")
plt.tight_layout()
plt.show()

Visualize it

A pie chart divides a whole into slices, where each slice’s angle is proportional to its share of the total — so all the slices together make up 100%. Watch it build slice by slice:

sketch A pie chart splits a whole into slices p5.js

Each slice's angle is proportional to its share of the total; together they add up to 100%.

Better alternative

If your goal is comparison, use a bar chart.

Continue to Subplots and Figure Size to combine several charts into one dashboard.

Pie Chart

A warning about pie charts

Basic pie chart

Improve readability

Visualize it

Better alternative

Next

🧪 Try It Yourself

Exercise 1 – Slices sum to 100%

Exercise 2 – Explode the biggest slice

Exercise 3 – Convert to a bar chart instead

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