2.5 rem equals 40 pixels.
This result assumes a root font size of 16 pixels, which is the default for most browsers. Since 1 rem equals the root font size, multiplying 2.5 by 16 gives the pixel value.
Conversion Tool
Result in pixel:
Conversion Formula
The formula to convert rem to pixels is:
pixels = rem × root font size
Since rem (root em) units always refer to the root element’s font size, which is mostly 16 pixels by browser default, you multiply the rem value by 16. This calculation makes the size consistent across pages regardless of the element’s own font size.
Example calculation for 2.5 rem:
- Root font size = 16 pixels
- Multiply: 2.5 × 16 = 40 pixels
- Therefore, 2.5 rem = 40 pixels
Conversion Example
- Convert 3 rem to pixels:
- Root font size: 16 pixels
- Calculation: 3 × 16 = 48 pixels
- Result: 3 rem equals 48 pixels
- Convert 1.75 rem:
- Root font size: 16 pixels
- Calculation: 1.75 × 16 = 28 pixels
- Result: 1.75 rem equals 28 pixels
- Convert 0.5 rem:
- Root font size: 16 pixels
- Calculation: 0.5 × 16 = 8 pixels
- Result: 0.5 rem equals 8 pixels
- Convert 4.2 rem:
- Root font size: 16 pixels
- Calculation: 4.2 × 16 = 67.2 pixels
- Result: 4.2 rem equals 67.2 pixels
Conversion Chart
This chart shows rem values from -22.5 to 27.5 and their equivalent pixel values assuming a 16-pixel root font size. Negative values can be useful in certain CSS scenarios, like relative positioning or transformations, even though negative font sizes are nonsensical.
| Rem | Pixels |
|---|---|
| -22.5 | -360 |
| -20.0 | -320 |
| -17.5 | -280 |
| -15.0 | -240 |
| -12.5 | -200 |
| -10.0 | -160 |
| -7.5 | -120 |
| -5.0 | -80 |
| -2.5 | -40 |
| 0.0 | 0 |
| 2.5 | 40 |
| 5.0 | 80 |
| 7.5 | 120 |
| 10.0 | 160 |
| 12.5 | 200 |
| 15.0 | 240 |
| 17.5 | 280 |
| 20.0 | 320 |
| 22.5 | 360 |
| 25.0 | 400 |
| 27.5 | 440 |
Related Conversion Questions
- How many pixels are 2.5 rem with a 20px root font size?
- What is the pixel equivalent of 2.5 rem in CSS?
- Does 2.5 rem always equal 40 pixels?
- How to calculate pixels from 2.5 rem if the root font changes?
- Why is 2.5 rem not matching 40 pixels on my webpage?
- Can 2.5 rem be negative pixels in CSS?
- What’s the difference between em and rem for 2.5 units?
Conversion Definitions
rem: The rem unit in CSS means “root em” and represents the font size of the root element (usually <html>). Unlike em, rem values do not depend on the parent’s font size but are always relative to the root, making styling consistent and scalable across a page.
pixel: A pixel is a single point in a raster image or on a computer screen. In CSS, pixels are absolute length units used to define sizes and measurements on screens, representing the smallest addressable element of a display device, although actual size can vary by screen resolution.
Conversion FAQs
What happens if the root font size is changed from 16px?
If the root font size changes, the pixel equivalent for rem units changes too. For example, if the root font size is 20px, then 2.5 rem would be 2.5 × 20 = 50 pixels instead of 40. This allows for scalable designs but requires awareness of the root size.
Can rem units be fractional and still convert properly?
Yes, rem units can be fractional like 2.5 or 1.75, and when converting to pixels, the multiplication with the root font size can result in decimals. Browsers handle fractional pixels by rounding or anti-aliasing, so visual rendering remains smooth.
Why might 2.5 rem not equal 40 pixels in some browsers?
Some browsers or devices might have different default root font sizes or user settings overriding them, causing 1 rem to differ from 16 pixels. Additionally, zoom settings or CSS overrides for <html> font size can cause variations in rem to pixel conversion.
Is rem unit better than px for responsive design?
Rem units allow text and layout to scale relative to the root font size, making it easier to adjust entire page sizing by changing one value. Pixels are fixed and don’t scale automatically, so rem units offer more flexibility for responsive design across devices.
Can rem units be negative in CSS, and what happens to pixel conversion?
Negative rem values are valid in CSS for properties that accept negative lengths, like margins or translations. When converting, negative rem values multiply with the root font size resulting in negative pixel values, which can be useful for positioning but not for font sizes.