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If you ever used CSS, you’ve probably seen px and rem units floating around. But what do they mean? And more importantly, which one should you use when designing your website? Let’s break it down in a way that actually makes sense.
Pixels (px)
Pixels are an absolute unit in CSS, meaning they represent a fixed size. When you define an element’s width, height, or font size in pixels, it stays exactly that size regardless of the screen size or user settings.
Why Use Pixels?
✅ Precision – You have complete control over the exact size of elements.
✅ Consistency – The design looks the same across all devices (at least visually).
The Problem with Pixels
The issue? Pixels don’t scale. If a user has a larger default font size set in their browser for accessibility, a pixel-defined font won’t adjust to their needs. That’s where rem comes in.
REM (Root EM)
Unlike pixels, rem (which stands for Root EM) is a relative unit based on the font size of the root element (html).
By default, most browsers set the root font size to 16px. That means:
1rem = 16px
2rem = 32px
0.5rem = 8px
Why Use REM?
✅ Scalability – If you change the root font size, everything adjusts proportionally.
✅ Accessibility – Users can modify text sizes based on their needs.
✅ Better responsiveness – It’s easier to create designs that adapt to different screen sizes.
When to Use Pixels vs. REM?
There’s no one-size-fits-all answer, but here’s a general rule of thumb:
✅ Use rem for font sizes – Ensures better accessibility and scalability.
✅ Use px for fixed elements – Icons, borders, and precise UI elements benefit from pixel precision.
Converting Pixels to REM in Webflow
Not great at math? No problem. If you’re using Webflow, the platform makes it easy to convert px to rem directly in the designer. Just enter /16 after your pixel value (e.g., 32/16), and Webflow will handle the conversion.
Or, you can use an online converter like NekoCalc.
Final Thoughts
Both px and rem have their place in web design. Pixels give you control, while rem makes your design more adaptable and user-friendly. If accessibility and scalability are important to you (which they should be), rem is the way to go, especially for typography.