REM value
1.5rem
Relative to root font size.
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CSS unit converter
REM & EM to PX Converter
Convert pixels into rem, em, and percent values with custom root and parent font sizes for CSS work.
Convert PX to REM and EM
Enter a pixel value and adjust the root or parent size to generate CSS-ready units.
EM value
1.5em
Relative to parent font size.
Percent
150%
Original pixels
24px
CSS example
.element {
font-size: 1.5rem;
padding: 1.5em;
}CSS workflow
When rem, em, and px give different answers
The converter is most useful when a spacing or typography value needs to move between design specs, component code, and a real CSS system without losing scale logic along the way.
Use rem when the value should scale with the root document size. That is usually the safest choice for page-level typography, spacing tokens, and layouts that need to remain predictable even when components live in different parts of the interface. If a team maintains a design token system, rem values are often the easiest numbers to keep consistent across screens.
Use em when the value should follow the surrounding component context instead of the whole page. That makes em helpful for buttons, cards, menus, and local spacing systems where the component may grow or shrink with its own font size. The tradeoff is that nested components can compound the value faster than people expect, which is why conversion tools are useful during review.
Use px when the value is truly fixed or when the conversation is still happening in absolute design measurements. Borders, hairlines, icon alignment, and a few tightly controlled UI details often stay easier to reason about in pixels. The risk is that px values can quietly drift away from the scaling behavior the rest of the system expects if they are used too broadly.
This page helps when a designer says "make this 24px," a developer needs the equivalent rem token, and the final component also has an em-based local scale. The conversion itself is simple math, but the right unit depends on what should stay fixed, what should inherit, and which part of the interface owns the scaling decision.
Frequently asked questions
What is 1rem in pixels?
With the common browser default of 16px root size, 1rem equals 16px.
What is the difference between rem and em?
REM is relative to the root element font size, while EM is relative to the current or parent font size.
Should I use rem or px?
Use rem for scalable typography and spacing, and px for precise fixed details when needed.
Why does em sometimes compound?
Nested elements can inherit changed font sizes, so em-based values can multiply across component levels.
Guide collection
Related guides
Use these supporting guides to understand the tool result and next testing steps.
Related tools
Continue with another ScreenMetricLab utility.
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