Free PX to EM Converter
What is px?
px stands for pixels. It is a fixed unit in CSS that represents a single dot on the screen.
padding: 10px;
What is em?
em is a relative unit based on the font size of the parent element.
padding: 2em;
Why convert px to em?
- Responsiveness:
emadapts to different screen sizes. - Accessibility: Users who zoom or use large fonts benefit from
em. - Scalability: Changing parent font-size scales child elements too.
- Consistency: Helps maintain layout ratios and readability.
Example: px vs em
body {
font-size: 16px;
}
h1 {
font-size: 32px;
}
body {
font-size: 16px;
}
h1 {
font-size: 2em;
}
If you change body font-size to 20px, the h1 will automatically scale to 40px.
Summary:
- Use
pxwhen you need absolute precision. - Use
emfor responsive, scalable, and accessible design.
What is PX to EM Conversion?
A Pixel (PX) to EM converter is an essential tool for modern responsive web design. In CSS, pixels are an absolute measurement unit representing physical dots on a screen, whereas EM is a relative unit relative to the font-size of the element's parent. Converting absolute values to relative EM units allows your text, margins, padding, and layout dimensions to scale dynamically and harmoniously.
The Mathematical Formula
Converting pixels to EM requires dividing the target pixel value by the base font size of the parent element (usually the browser default base size of 16px):
EM = Pixels (PX) ÷ Base Font Size
For example, if your base font size is 16px and you want to convert a design requirement of 24px into EM:
Common PX to EM Conversion Table (Base 16px)
Use this handy reference table for the most common typography and layout sizes assuming a default base font size of 16px:
| Pixels (PX) | Base Size (PX) | Result in EM |
|---|---|---|
| 8 px | 16 px | 0.5 em |
| 12 px | 16 px | 0.75 em |
| 14 px | 16 px | 0.875 em |
| 16 px | 16 px | 1.0 em |
| 20 px | 16 px | 1.25 em |
| 24 px | 16 px | 1.5 em |
| 32 px | 16 px | 2.0 em |
| 48 px | 16 px | 3.0 em |
| 64 px | 16 px | 4.0 em |
EM vs. REM Units: When to Use Which?
Both EM and REM are relative units in CSS, but they calculate relative values differently:
- EM (Element-Relative): Calculations are relative to the font-size of the element's direct parent. It is excellent for component-level modular spacing (such as padding inside a button relative to its text size).
- REM (Root-Relative): Calculations are relative strictly to the root
<html>element. This prevents typography compounding issues where text keeps shrinking or growing in nested elements.
As a rule of thumb, use REM for global layout grids, margins, and body typography, and reserve EM for design assets that should scale contextually inside a container.
