Px To Em Converter
Convert pixel (px) values to relative em units for scalable and accessible web design.
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Key Takeaway
The core difference is that px is an absolute unit (a fixed size) while em is a relative unit (its size depends on the font-size of its parent element). Understanding this is key to creating scalable and responsive web designs.
Understanding Px vs. Em
In web design, `px` (pixels) and `em` are two common units of measurement for sizing text, margins, and other elements. While they might seem interchangeable at first, their fundamental difference has a huge impact on accessibility and responsive design.
Pixels (px): The Absolute Unit
A pixel is a fixed-size unit. One pixel is equal to one dot on your screen. Because it's an absolute unit, `16px` will always be `16px` regardless of any other styling. This makes `px` very predictable and easy to control, which is why it's often used for things that should not scale, like borders or fixed-width containers.
Em: The Relative Unit
The `em` unit is relative. Its value is based on the font-size of the parent element. For example, if a parent container has a `font-size` of `16px`, then for any child element, `1em` is equal to `16px`. If you set a child's font-size to `1.5em`, its computed size will be `24px` (1.5 * 16px).
This relativity is powerful because it allows you to create scalable layouts. If a user changes their browser's base font size for better readability, all elements sized with `em` units will scale up or down accordingly, providing a much better user experience.
Practical Example: Px vs. Em
Imagine you have a base font size of `16px` on the body of your page.
| CSS Rule | Computed Size | Explanation |
|---|---|---|
font-size: 16px; | 16px | Fixed size, will not change. |
font-size: 1em; | 16px | 1 times the parent font size (1 * 16px). |
font-size: 2em; | 32px | 2 times the parent font size (2 * 16px). |
font-size: 0.75em; | 12px | 0.75 times the parent font size (0.75 * 16px). |
The standard browser default font-size is 16px, which is why it's used as the base in these calculations.
Frequently Asked Questions (FAQ)
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