REM to Percent Converter

REM

Percent (%)

How to Use REM to Percent Converter

Enter Your Value: Type your rem value (like 1.25) into the “REM” field.
See the Magic: The “Percent (%)” field will automatically show you the equivalent percentage (like 125).
Copy and Go: Use the “Copy %” or “Copy REM” buttons to grab the value you need for your stylesheet. The “Reset” button clears both fields for your next conversion.

REM to Percent Conversion Formula

While the tool does the work for you, the math is refreshingly simple. It’s based on the idea that 1rem is equivalent to 100% of the root element’s size.

The Formula:

To get Percent from REM: $Percent = REM \times 100$
To get REM from Percent: $REM = Percent / 100$

Example:

If you have 1.5rem, the formula is: 1.5 × 100 = 150%

If you have 80%, the formula is: 80 / 100 = 0.8rem

Common REM to Percent Conversion Table

Need a quick lookup? Here are some of the most common values you’ll use in web design.

REM Value	Percent (%) Value	Common Use Case
0.25rem	25%	Small spacing, borders
0.5rem	50%	Small-medium spacing
0.75rem	75%	Gaps, component padding
0.8rem	80%	Often used as small body text
1rem	100%	Baseline (default body text)
1.25rem	125%	Subheadings (h4, h5)
1.5rem	150%	Main headings (h2, h3)
2rem	200%	Large headings (h1)
2.5rem	250%	Hero section titles
3rem	300%	Extra-large display text

Understanding the “Why”: REM vs. Percent in CSS

This is the part that trips up many developers. While our tool shows a direct 1.5 = 150 conversion, in a real CSS file, 1.5rem and 150% can behave very differently.

What is REM?

Think of rem as your global ruler. It always looks at the root (<html>) element’s font-size.

By default, most browsers set the root font size to 16px.
So, 1rem = 16px, 1.5rem = 24px, etc.
Why it’s awesome: If a user changes their browser’s default font size (for accessibility), your entire site scales up or down perfectly. You get consistency and accessibility in one.

What is Percent (%)?

Think of % as your local ruler. It always looks at its direct parent element.

If a div has a font-size of 20px, a child p tag with font-size: 150% will be 30px (1.5 × 20).
If that same p tag was inside a div with font-size: 10px, it would only be 15px!
Why it’s tricky: This “compounding” or “nesting” effect is why percentages can sometimes give you unexpected results for font-size.

When Should You Use REM vs. Percent?

Here’s a simple cheat sheet:

Use rem for:
- Typography: font-size for your body text, headings, and paragraphs.
- Global Spacing: margin, padding, width, height on main layout components. This ensures your spacing and your text scale together.
Use % for:
- Fluid Layouts: Setting the width of a column (e.g., width: 50%) to make it responsive.
- Child Element Scaling: Making an element scale relative to its container. For example, an icon inside a button could have a height: 80% to always be 80% of the button’s height.

This tool is perfect for when you’re prototyping or trying to understand the baseline relationship between these two powerful units.

Frequently Asked Questions (FAQ)

Q: What is the default `rem` value in pixels?

A: In almost all modern browsers, the default root font-size is 16px. Therefore, 1rem = 16px by default.

Q: Is `1rem` always equal to `100%`?

A: No. This is the most important takeaway!

1rem is 100% of the root (<html>) element.
100% is 100% of the parent element. They only behave the same way if the parent element has the exact same font size as the root element.

Q: Is it better to use `rem`, `px`, or `%` for font sizes?

A: Most developers today prefer rem for font-size. It provides the most consistent and accessible results, as it respects the user’s browser font settings while avoiding the “compounding” problem of em and %. px is too rigid, and % can be unpredictable.

Q: What’s the difference between `em` and `rem`?

A: They are both relative units, but:

rem (Root EM): Is relative to the root element (<html>).
em (regular EM): Is relative to the parent element (just like %).

Related Tools