CSS Unit Converter
Convert CSS units instantly between pixels (px), rems, ems, points (pt), percentages (%), and other absolute or relative web sizes. Perfect for responsive web design.
What is the CSS Unit Converter?
Why use rem instead of px?
In modern web design, accessibility and responsive design are paramount. While pixels (px) are fixed-size units, rem (root em) and em are relative units.
- Accessibility: Using
remrespects a user's browser default font size. If a user with visual impairments increases their default font size, yourrem-based layout will scale gracefully, unlike a layout hardcoded withpx. - Responsive Scaling: You can proportionally scale your entire website by changing a single
font-sizeproperty on thehtmlelement using media queries, which is much more efficient than overriding individual pixel values.
How does Base Pixel Size work?
rem or % into a physical equivalent like px, the converter needs a reference point. This is the Base Pixel Size. By default, almost all browsers use a base size of 16px. If you specify 1rem, it equals 16px. If you change your website's root font size in CSS (e.g., html { font-size: 10px; }), you should update the Base Pixel Size in this converter to 10 for accurate results.
Frequently Asked Questions
1. What is the difference between rem and em?
'rem' (root em) is relative to the font-size of the root element (usually ), while 'em' is relative to the font-size of its direct or nearest parent element. Using 'rem' is generally safer for global layout consistency.
2. Why do I need to set a Base Pixel Size?
Relative units like 'rem', 'em', and '%' depend on a base font size to calculate their actual pixel value. The standard default base size in most browsers is 16px, but if you change this in your CSS, you should update it here for accurate conversions.
3. Should I use px or rem for my website?
It is widely recommended to use 'rem' for sizing (font-size, padding, margins) because it respects the user's browser font-size preferences, improving accessibility. Use 'px' for things that must remain a strict fixed size regardless of user preferences (like a 1px border).
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