Do You Know Why REM is the Ultimate Unit for Scalable and Responsive Design?
When it comes to web design, the choice of unit for measurements will make or break your project’s responsiveness and scalability. With so many options available — including pixels, percentages, ems, and viewport units — it’s no wonder why REM stands out as a difference-maker. Why? Well, it’s because REM combines the precision of absolute units with the flexibility of relative units, making it the perfect choice for modern web development.
Let’s dive into what REM is, why REM is so useful, and how it outshines other units with practical examples.
What is REM?
REM stands for “Root EM.” It’s a relative unit in CSS referring to the font size of the root element (mostly <html>). Most browsers set the root font size by default to 16 pixels unless you specify otherwise. So, if you use 1rem, it means 16px by default, and 2rem equals 32px.
The advantages of REM are that it does not rely on its parent element, just like “em”. Instead, it always resets to the root font size to maintain a consistent scaling in your design.
Why REM is Better than Pixels (px)?
Pixels are straightforward — 1px equals one pixel on the screen. While this might sound like the easiest option, it comes with some significant drawbacks:
- Lack of Scalability:
Pixels are absolute, so they don’t adjust when the user changes their browser’s default font size or zooms in/out.- Example: If a user with visual impairments increases their browser’s font size to improve readability, a layout defined in pixels remains fixed, making the text or spacing hard to read.
2. Responsiveness Issues:
- Modern devices come in various resolutions and sizes. Pixels can struggle to adapt seamlessly across these variations.
REM Solution: With REM, you define measurements relative to the root font size. If a user changes the default font size in their browser settings, the entire design scales accordingly. This makes your layout more accessible and adaptable.
REM vs. EM: Consistency Wins
While both REM and EM are relative units, they behave differently.
EMis relative to the font size of its parent element.REMis relative to the font size of the root element.
Example Problem with EM: Let’s say you nest multiple elements with font-size defined in EM:
body {
font-size: 16px;
}
.container {
font-size: 1.5em; /* 24px (16px * 1.5) */
}
.child {
font-size: 2em; /* 48px (24px * 2) */
}
In this case, the .child element’s font size becomes 48px instead of the expected 32px because EM multiplies font sizes based on its parent. This cascading behavior can lead to unexpected results.
REM Solution: With REM, you avoid this cascading problem entirely:
body {
font-size: 16px;
}
.container {
font-size: 1.5rem; /* 24px */
}
.child {
font-size: 2rem; /* 32px */
}
Now, the .child font size is always 32px, regardless of nesting.
How REM Excels in Responsive Design
REM is incredibly handy for creating fluid, responsive layouts because you can scale everything with a single adjustment to the root font size.
Example: Building a Responsive Layout
Imagine you’re designing a website where you want the font size and spacing to adjust automatically for different screen sizes.
Using REM, you can achieve this by setting a font-size on the <html> tag based on the viewport width:
