How is Font Size Measured? A Simple Guide!

If you’re new to design, you might wonder: how exactly is font size measured? Choosing the right font size is not only about making text look good, but also about ensuring readability, consistency, and user experience. In this article, we’ll explain in simple terms how font size works, the different measurement units, and tips to choose the right font size for your project.

Font size refers to the height of the text characters in your design or document. When you set font size to “12pt” or “16px”, you’re setting the vertical space that the text occupies from the top of the tallest character (ascender) to the bottom of the lowest part (descender). However, font size does not always represent the exact visual size of the letters, as different fonts can appear larger or smaller even at the same font size.

Traditionally, font size is measured in points (pt). One point equals 1/72 of an inch. This system was created during the print era and is still commonly used in printed materials today.

• Example: A font size of 12pt means the height of the letter is approximately 1/6 inch (12 divided by 72).

However, in digital design, font size is more commonly measured in:

• Pixels (px): Standard unit for web design. One pixel represents one dot on the screen.
• Em and Rem: Relative units, often used in CSS to make font sizes scalable and responsive.

Each unit has its purpose depending on the platform and project you’re working on.

One important thing to understand: font size doesn’t guarantee that two fonts will look exactly the same in size, even if they’re both set to 12pt or 16px. This is because each font has its own unique design characteristics, including:

• X-height: The height of lowercase letters like “x”. Fonts with a larger x-height will look bigger.
• Ascenders and Descenders: Parts of letters that rise above or drop below the baseline.
• Line Spacing or Leading: Additional space between lines that can make text look more open or compact.

This is why, for example, a 12pt serif font may look smaller than a 12pt sans serif font.

In digital design, using pixels (px) is more common than points. This is because screens display content based on pixels, making it easier to control and adjust font sizes using px units.

Here’s a simple comparison:

• Print Design: Use points (pt).
• Web Design: Use pixels (px), em, or rem.

Modern web developers prefer using em and rem for better scalability. These units adjust based on the user’s default browser settings, making websites more accessible.

Example:

• 1em = current font size.
• 1rem = root font size.

Choosing the right font size depends on the type of content and medium:

• Body Text (Print): 10pt to 12pt is standard.
• Body Text (Web): 14px to 16px is recommended for easy reading.
• Headings (Print): 18pt to 36pt depending on importance.
• Headings (Web): 24px to 48px or larger.

Always consider your audience. For mobile users, slightly larger font sizes can improve readability.

1. Test Across Devices: Ensure your text looks readable on desktops and mobile.
2. Prioritize Accessibility: Larger font sizes help users with visual impairments.
3. Consistent Hierarchy: Use clear font size differences between headings, subheadings, and body text.
4. Avoid Using Too Many Fonts: Focus on 1–2 font families and adjust sizes for hierarchy instead.
5. Consider Line Height: Good line spacing improves readability.

Now you know how font size is measured! Whether you're working on print materials using points (pt) or designing websites with pixels (px), understanding font size measurement is essential to create professional and readable designs. Keep in mind that different fonts may look different at the same size, so always preview your design before finalizing.

Font size might seem like a small detail, but it has a big impact on user experience. The right font size can help your audience read easily, understand your message, and enjoy your design.