FAQ
Common px to rem conversion questions
These are the questions users most often ask when converting CSS units or checking which unit is right for a layout.
How do I convert px to rem?
Divide the pixel value by the root font size. With a 16px base, 16px equals 1rem and 24px equals 1.5rem.
How do I convert rem to px?
Multiply the rem value by the root font size. With a 16px base, 2rem equals 32px.
What is the difference between rem and em?
rem is relative to the root font size of the page, while em is relative to the font size of the current element or parent context.
Why does the base font size matter?
The base font size determines the ratio between px and relative units. If your project uses a root size other than 16px, conversions need to use that value to stay accurate.
Can I use this calculator for print units like pt, mm, and cm?
Yes. The converter supports common print and physical units, which helps when translating between CSS layouts, PDFs, and print specs.
Which unit should I use in CSS?
Use rem for scalable typography and spacing systems, em for component-local scaling, px for precise UI measurements, and percent or physical units when the layout depends on context or print output.