Comparing Units (specifically For Font Size)
Introduction
Font size refers to the size of the characters in a typeface. It is typically measured in points, with one point equal to 1/72 of an inch.
Font size is an important aspect of design because it can greatly impact the readability, legibility of text, and beauty of a design. An ill-chosen font size gives a poor design or illegible text and negatively affects the text's readability. This causes a poor user experience.
Examples of units used in font size are Pixel (px), Point(pt), Rem(Rem), Em(em), and Percentage(%).
In this article, you would understand the difference between each unit, how to calculate them, and when to use each unit.
Units Used In Font-Size
- Pixels (px)
A pixel, often abbreviated as "px," is a screen-based unit of measurement. The size of a font in pixels is determined by the number of pixels tall and wide each character takes up on the screen. When designing digital displays, it is common to use pixels as the unit of measurement for font size because the resolution of the display is often fixed and the number of pixels on the screen is known.
To calculate the font size in pixels, you can use the following formula:
Font size (px) = (point size \ resolution) / 72*
Where "point size" is the size of the font in traditional print measurements, and "resolution" is the number of pixels per inch (PPI) of the display. For example, to set the font size to 16 pixels, the code would be:
body {
font-size: 16px;
}
- Ems (em)
An "em" is a relative unit of measurement for font size in web design. It is a relative unit, meaning that it is based on the current font size of the parent element. The size of 1em is equal to the current font size of the parent element. For example, if the parent element has a font size of 16 pixels, then 1em is equal to 16 pixels.
When designing for the web, it's common to use em as a unit of measurement for font size because it allows for more flexibility and adaptability to different screen sizes. Since it's relative, when you change the font size of the parent element, all elements with em values will be scaled accordingly, making it easy to create a responsive design.
To calculate the font size in em, you can use the following formula:
Font size (em) = point size/parent font size
Where "point size" is the size of the font in traditional print measurements, and "parent font-size" is the current font size of the parent element.
For example, to set the font size to 1.5 times the size of the parent element, the code would be:
body {
font-size: 1em;
}
p {
font-size: 1.5em;
}
It's important to note that the default font size for the HTML element is 16px so 1em = 16px.
- Rem (root em)
A "rem" (root em) is a relative unit of measurement for font size in web design. It is similar to the "em" unit, but it is not affected by the font size of any parent elements. It is always relative to the font size of the root element (usually the <html> element) rather than the current font size of the parent element. This means that if the root element's font size is changed, all elements with rem values will be scaled accordingly.
When designing for the web, using Rem as a unit of measurement for font size is a good choice because it allows for more consistency and predictability in your design. Since it's always relative to the root element, it's easy to set a base font size and then scale all other font sizes relative to it. It is also commonly used along with media queries to create responsive designs.
To calculate the font size in rem, you can use the following formula:
Font size (rem) = point size/root font size
Where "point size" is the size of the font in traditional print measurements, and "root font-size" is the current font size of the root element.
For example, to set the font size to 1.5 times the size of the root element, the code would be:
HTML {
font-size: 16px;
}
p {
font-size: 1.5rem;
}
It's important to note that the default font size for the root element (HTML) is 16px so 1rem = 16px, and it's accessible via CSS using the font-size property on the root element.
It's also worth noting that, unlike pixels and em, rem units are independent of the parent-child hierarchy, which makes them more predictable and consistent in responsive designs.
- Percentage (%)
A relative unit of measurement that is based on the font size of the parent element. A font size of 100% is equal to the font size of the parent element. This unit is commonly used in web design because it allows text to scale with the user's preferences or device. A percentage is a relative unit of measurement that is based on the font size of the parent element.
It's common to use percentage as a unit of measurement for font size in web designing because it allows for more flexibility and adaptability to different screen sizes. Since it's relative, when you change the font size of the parent element or the root element, all elements with percentage values will be scaled accordingly, making it easy to create a responsive design.
To calculate the font size in percentage, you can use the following formula:
Font size (%) = (point size/parent font size) \ 100*
Where "point size" is the size of the font in traditional print measurements, and "parent font-size" is the current font size of the parent element or the root element.
For example, to set the font size to 150% of the parent element, the code would be:
body {
font-size: 16px;
}
p {
font-size: 150%;
}
It's important to note that the default font size for the root element (HTML) is 16px so 100% = 16px.
It's also worth noting that percentage units are more predictable and consistent in responsive designs, as they are based on the default font size of the root element, and also, they can be used to create scalable layouts.
Comparison Of Font-Size Units
The differences between the units include the following but are not limited to:
S/N | Pixel (px) | Em (em) | Rem (rem) | Percentage (%) |
1 | Fixed unit of measurement that is based on the resolution of the display | Relative unit of measurement that is based on the current font size of the parent element | Relative unit of measurement that is based on the font size of the root element | Relative unit of measurement that is based on the current font size of the parent element or the default font size of the root element |
2 | Allows for precise control over font size allows | Allows for flexibility and adaptability to different screen sizes. | Allows for consistency and predictability in your design. | Allows for flexibility and adaptability to different screen sizes and it's more predictable and consistent in responsive designs |
3 | It can be inflexible, as it doesn't adjust to different screen sizes. | It can be difficult to predict the final font size, as it depends on the font size of the parent element | It can be difficult to control the final font size, as it depends on the font size of the root element. | It can be difficult to control the final font size, as it depends on the font size of the parent element or the root element. |
Conclusion
The choice of unit for font size in web design depends on the specific requirements of the project and the target audience. Pixel (px) is a fixed unit of measurement that allows for precise control over font size, but it can be inflexible. Em (em) and rem (rem) are relative units of measurement that allow for flexibility and adaptability to different screen sizes. Percentage (%) is a relative unit of measurement that allows for flexibility and adaptability to different screen sizes, and it's more predictable and consistent in responsive designs.
When selecting a unit of measurement for font size, it's important to consider the specific requirements of the project and the target audience, and the best practices for creating responsive designs. It's recommended to use media queries and a mobile-first approach to adjust the font size based on the screen size of the device.