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Screen pixel density
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Calculators / Technology / Pixels and rem conversion
Pixels and rem conversion calculator
Express a CSS pixel size in rem using the actual root font size.
On this page
Size in rem1.5rem
Root-relative percentage150%
Calculator controls
How to calculate
Express a CSS pixel size in rem using the actual root font size.
Size in rem =
pixels/root remRoot-relative percentage =
pixels/root*100 %Worked example
- CSS size (px): 24
- Root font size (px): 16
- Size in rem: 1.5 rem
- Root-relative percentage: 150 %
Assumptions and limits
CSS pixels are layout units, not device pixels. The root size is supplied by you; browser preferences and styles may change it.
Results are rounded for display; calculations use unrounded values. Read our calculation methodology.
Understanding the result
Express a CSS pixel size in rem using the actual root font size. A 24 px size at a 16 px root is 1.5 rem. Changing the root while keeping rem fixed changes the rendered CSS size.
When this tool is useful
A 24 px size at a 16 px root is 1.5 rem. Changing the root while keeping rem fixed changes the rendered CSS size.
Understanding your inputs
| Input | Example |
|---|---|
CSS size (px) pixels | 24 |
Root font size (px) root | 16 |
Frequently asked questions
What assumptions should I check?
CSS pixels are layout units, not device pixels. The root size is supplied by you; browser preferences and styles may change it.
How can I check the result?
Start with the labelled example. Keep units consistent, calculate without intermediate rounding and change one input at a time. The diagram explains the model; the result table supplies the numerical answer.