How to Set Font Size in Matplotlib: Simple Guide

You can set font size in Matplotlib by using the fontsize parameter in functions like plt.title(), plt.xlabel(), and plt.ylabel(). For tick labels, use plt.xticks(fontsize=) and plt.yticks(fontsize=). You can also set a global font size using plt.rcParams['font.size'].

Syntax

Here are common ways to set font size in Matplotlib:

• plt.title('Title', fontsize=12): Sets font size of the plot title.
• plt.xlabel('X-axis', fontsize=10): Sets font size of the x-axis label.
• plt.ylabel('Y-axis', fontsize=10): Sets font size of the y-axis label.
• plt.xticks(fontsize=8): Sets font size of x-axis tick labels.
• plt.yticks(fontsize=8): Sets font size of y-axis tick labels.
• plt.rcParams['font.size'] = 14: Sets default font size globally for all text.

python

import matplotlib.pyplot as plt

plt.rcParams['font.size'] = 14  # global font size

plt.title('Title', fontsize=12)
plt.xlabel('X-axis', fontsize=10)
plt.ylabel('Y-axis', fontsize=10)
plt.xticks(fontsize=8)
plt.yticks(fontsize=8)

Example

This example shows how to set font sizes for title, axis labels, and tick labels in a simple line plot.

python

import matplotlib.pyplot as plt

x = [1, 2, 3, 4]
y = [10, 20, 25, 30]

plt.plot(x, y)
plt.title('Sample Plot', fontsize=16)
plt.xlabel('X Axis Label', fontsize=14)
plt.ylabel('Y Axis Label', fontsize=14)
plt.xticks(fontsize=12)
plt.yticks(fontsize=12)

plt.show()

Output

A line plot with a large title, axis labels, and tick labels all showing different font sizes as set.

Common Pitfalls

Common mistakes when setting font size in Matplotlib include:

• Forgetting to use the fontsize parameter inside text functions like plt.title().
• Trying to set font size directly on tick labels without using plt.xticks() or plt.yticks().
• Setting plt.rcParams['font.size'] after plotting, which won't affect existing text.
• Confusing size with fontsize parameter names (always use fontsize).

Example of wrong and right ways:

python

import matplotlib.pyplot as plt

x = [1, 2, 3]
y = [4, 5, 6]

plt.plot(x, y)
# Wrong: font size ignored
plt.title('Wrong Title', size=20)  # 'size' is not recognized

# Right:
plt.title('Right Title', fontsize=20)
plt.show()

Output

Plot showing the title with correct font size only for the right example.

Quick Reference

Function/Parameter	Purpose	Example
plt.title()	Set title text and font size	plt.title('Title', fontsize=16)
plt.xlabel()	Set x-axis label and font size	plt.xlabel('X Label', fontsize=12)
plt.ylabel()	Set y-axis label and font size	plt.ylabel('Y Label', fontsize=12)
plt.xticks()	Set font size of x-axis tick labels	plt.xticks(fontsize=10)
plt.yticks()	Set font size of y-axis tick labels	plt.yticks(fontsize=10)
plt.rcParams['font.size']	Set global default font size	plt.rcParams['font.size'] = 14

Key Takeaways

Use the fontsize parameter inside text functions like plt.title() to set font size.

Set tick label font size with plt.xticks(fontsize=) and plt.yticks(fontsize=).

Use plt.rcParams['font.size'] to set a global font size before plotting.

Avoid using incorrect parameter names like size instead of fontsize.

Set font sizes before calling plt.show() to see the changes.