PX to REM Converter - Free Online Pixel to REM Calculator

Need to convert px to rem for your web projects? You’re in the right place.

Here’s the deal:

Our free px to rem converter gives you instant, accurate conversions. No manual calculations. No guesswork.

How to Use This PX to REM Converter

Using this tool is straightforward:

Enter a value - Type your pixel or rem value in either input field
Select your base font size - Choose from 6px to 32px using the dropdown menu (default is 16px)
Get instant results - The conversion happens automatically as you type

Want to know the best part?

This is a bidirectional converter. You can convert px to rem OR rem to px - just enter your value in either field and the other updates instantly.

Pro tip: Make sure to set the correct base font size that matches your project’s root font-size. This ensures accurate px to rem conversions.

What Is PX (Pixel)?

PX stands for pixels - the most basic unit of measurement in digital screens.

Here’s what you need to know:

1px = one physical dot on your screen
Pixels are absolute units - they don’t change based on other elements
Most design tools (Figma, Sketch, Photoshop) export measurements in pixels

But here’s the kicker:

Fixed pixel values don’t scale well. When users change their browser font size for accessibility, px-based layouts stay rigid.

What Is REM?

REM stands for “Root EM” - a relative CSS unit based on the root element’s font size.

Now:

If your <html> element has font-size: 16px, then:

1rem = 16px
2rem = 32px
0.5rem = 8px

The key insight:

REM values scale proportionally when the root font size changes. This makes your entire layout responsive to user preferences.

PX vs REM: Why Use REM?

Here’s a comparison between px and rem units:

Feature	PX	REM
Type	Absolute	Relative
Scalability	❌ Fixed size	✅ Scales with root font
Accessibility	❌ Ignores user settings	✅ Respects user preferences
Maintenance	❌ Change each value manually	✅ Adjust root font, all scales
Predictability	✅ Always same size	✅ Consistent across components

It gets better:

Using rem for your px to rem conversions provides these benefits:

Better accessibility - Users who increase browser font size get larger text
Easier responsive design - Change one value, scale everything
Consistent spacing - All elements maintain proportional relationships
Future-proof - Works well with modern CSS and design systems

How PX to REM Conversion Works

The px to rem formula is simple:

rem = px ÷ base-font-size

For example, with a 16px base font:

16px ÷ 16 = 1rem
24px ÷ 16 = 1.5rem
32px ÷ 16 = 2rem
8px ÷ 16 = 0.5rem

To convert rem back to px:

px = rem × base-font-size

This is crazy:

Some developers set their base to 62.5% (10px) to make mental math easier. With 10px base: 16px = 1.6rem, 20px = 2rem, 14px = 1.4rem.

Common PX to REM Conversion Table

Here are the most frequently used px to rem conversions (base 16px):

Pixels	REM	Common Use Case
4px	0.25rem	Hairline borders, micro spacing
8px	0.5rem	Small gaps, icon padding
12px	0.75rem	Small text, captions, labels
14px	0.875rem	Secondary text, compact body
16px	1rem	Default body text
18px	1.125rem	Large body text
20px	1.25rem	H4 headings, lead text
24px	1.5rem	H3 headings
32px	2rem	H2 headings
48px	3rem	H1 headings
64px	4rem	Hero text, display headings

Frequently Asked Questions

What’s the difference between REM and EM?

REM is relative to the root <html> element’s font size. EM is relative to the parent element’s font size. REM is more predictable because it always references the same base value, while EM can compound and become confusing in nested elements.

What’s the default base font size for px to rem conversion?

Most browsers default to 16px as the root font size. Our px to rem converter uses 16px as default, but you can change it to match your project.

Should I always use 16px as the base?

No. Use whatever fits your design system. Common choices:

10px (62.5%) - Easier mental math
14px - Compact designs
16px - Browser default
18px - High readability

How do I set the base font size in CSS?

Here’s how to set your base font size:

/* Method 1: Using pixels (16px default) */
html {
  font-size: 16px;
}

/* Method 2: Using percentage (62.5% = 10px) */
html {
  font-size: 62.5%;
}

/* Method 3: Using clamp for responsive base */
html {
  font-size: clamp(14px, 2vw, 18px);
}

Pro tip:

Using percentage (like 62.5%) respects user browser settings better than fixed pixels. If a user sets their browser to larger text, percentage-based roots will scale accordingly.

Will rem units work in older browsers?

REM is supported in all modern browsers including IE9+. For very old browsers, you can provide px fallbacks, but this is rarely needed today.

When should I use px instead of rem?

Use pixels for:

Borders - 1px borders should stay crisp
Box shadows - Often look better with fixed values
Media queries - Define breakpoints in px for consistency

Use rem for:

Font sizes - Always
Spacing (margin, padding) - For scalable layouts
Component dimensions - When you want proportional scaling