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PX to Percent Converter

Convert pixels to percentage units instantly with our free px to percent calculator for responsive design and fluid layouts.

px
px
%

(600px ÷ 1200px) × 100 = 50%

Width of the parent element in pixels

How to Use Our PX to Percent Converter

Converting px to percentage is simple with our calculator. Learn how to convert pixels to percentage units for responsive web design in three easy steps.

1

Set Parent Container Width

Enter the width of the parent container in pixels. This is the reference width used to calculate the percentage value.

2

Enter Pixel Value

Type the pixel value you want to convert. The converter accepts whole numbers and decimals for precise measurements.

3

Get Percentage Result

The converter instantly calculates the percentage value. Copy the result and use it in your CSS for responsive, fluid layouts.

PX to Percent: Understanding the Difference

Before using our px to percent converter, learn the key differences between pixels and percentage units for responsive design and fluid layouts.

What are Pixels (PX)?

Fixed Size Unit

Pixels are absolute units that stay the same size regardless of parent container size. 200px is always 200px.

Limited Flexibility

Pixel-based widths don't adapt to different screen sizes, making responsive design more challenging.

Best Use Cases

Ideal for borders, fixed-width elements, and designs where precise control is needed.

What are Percentage Units?

Relative to Parent

Percentage values are calculated relative to the parent container's width. If the parent is 1200px, then 50% equals 600px.

Fluid Layouts

Percentage units automatically adapt when container sizes change, making them perfect for responsive design and flexible layouts.

Responsive Benefits

Percentage-based layouts scale smoothly across different screen sizes without media query adjustments.

PX to Percent Conversion Formula

% = (Pixels ÷ Parent Width) × 100

Parent width is the container's width in pixels

Example: 600px ÷ 1200px × 100 = 50%

Example: 300px ÷ 1200px × 100 = 25%

Example: 900px ÷ 1200px × 100 = 75%

Step-by-Step Calculation Example

Step 1: Identify your pixel value → 400px

Step 2: Identify parent container width → 1200px

Step 3: Divide pixel by parent width → 400 ÷ 1200 = 0.3333

Step 4: Multiply by 100 → 0.3333 × 100 = 33.33%

Result: 400px = 33.33% of 1200px container

PX to Percent Conversion Reference Table

Quick reference tables for common pixel to percentage conversions. Use these as a guide for your responsive designs with different container widths.

Parent: 1200px

PixelsPercent
100px8.33%
200px16.67%
300px25%
400px33.33%
500px41.67%
600px50%
800px66.67%
900px75%
1000px83.33%
1200px100%

Parent: 1000px

PixelsPercent
100px10%
200px20%
250px25%
300px30%
400px40%
500px50%
600px60%
750px75%
800px80%
1000px100%

Parent: 800px

PixelsPercent
100px12.5%
200px25%
240px30%
300px37.5%
400px50%
480px60%
500px62.5%
600px75%
640px80%
800px100%

💡Pro Tip: Using Conversion Tables

These reference tables are perfect for quick lookups when building responsive layouts. Remember that percentages are always relative to the parent container's width, so choose the table that matches your design's container size. For custom values, use our converter tool above.

Real-World CSS Examples

See how to implement pixel to percentage conversions in actual CSS code for common responsive design scenarios.

❌ Fixed Width (Pixels)

.container {
  width: 1200px;
  margin: 0 auto;
}

.sidebar {
  width: 300px;
  float: left;
}

.main-content {
  width: 900px;
  float: right;
}

This fixed-width layout doesn't adapt to different screen sizes and may cause horizontal scrolling on smaller devices.

✓ Fluid Width (Percentage)

.container {
  width: 100%;
  max-width: 1200px;
  margin: 0 auto;
}

.sidebar {
  width: 25%; /* 300px ÷ 1200px × 100 */
  float: left;
}

.main-content {
  width: 75%; /* 900px ÷ 1200px × 100 */
  float: right;
}

This fluid layout scales proportionally and adapts to any container width, perfect for responsive design.

3-Column Grid Layout

/* Parent container: 1200px */
.grid-container {
  width: 100%;
  max-width: 1200px;
}

.grid-item {
  width: 33.33%; /* 400px ÷ 1200px × 100 */
  padding: 15px;
  box-sizing: border-box;
  float: left;
}

Each column takes up exactly one-third of the container, automatically adjusting to the parent's width.

Responsive Image Container

.article-container {
  width: 100%;
  max-width: 800px;
}

.featured-image {
  width: 100%; /* Full width of parent */
  height: auto;
}

.image-caption {
  width: 87.5%; /* 700px ÷ 800px × 100 */
  margin: 0 auto;
  padding: 10px 0;
}

Images scale to fit their container while captions maintain proportional width for optimal readability.

⚠️Common Mistakes to Avoid

×

Forgetting box-sizing

Always use box-sizing: border-box when using percentage widths with padding/borders to prevent layout breaks.

×

Using percentage height without explicit parent height

Percentage heights only work when the parent element has a defined height. Use viewport units (vh) or flexbox for vertical sizing instead.

×

Mixing units incorrectly

When using percentages, ensure all sibling elements' widths add up to 100% (or less) to prevent wrapping issues.

×

Ignoring rounding errors

Percentages like 33.33% × 3 = 99.99%, not 100%. Use calc() for precise calculations: width: calc(100% / 3)

When to Use PX to Percent Conversion

Knowing when to convert px to percent is essential for CSS best practices. Use our px to percent converter for these common scenarios.

Use Percentage For:

  • ✓Fluid grid layouts and column widths
  • ✓Responsive container widths
  • ✓Elements that should scale with their parent
  • ✓Multi-column layouts without fixed widths
  • ✓Adaptive designs across screen sizes

Use Pixels For:

  • •Borders and border widths
  • •Box shadows and outline styles
  • •Fixed-size icons and images
  • •Font sizes (use rem or em instead)
  • •Elements that should never scale

PX to Percent Converter FAQ

Common questions about our px to percent calculator and converting pixels to percentage units in CSS.

How do I convert PX to percent?

To convert px to percent, divide the pixel value by the parent container's width, then multiply by 100. The formula is: % = (px ÷ parent width) × 100. For example, if you have a 600px element inside a 1200px container: 600 ÷ 1200 × 100 = 50%. Our px to percent converter does this calculation automatically.

Why use percentage instead of pixels?

Percentage units create fluid, responsive layouts that adapt to different screen sizes automatically. When you convert px to percent, your elements scale proportionally with their parent container, making your design more flexible. This is especially useful for responsive web design, where elements need to adjust across mobile, tablet, and desktop views.

What is the parent width in percentage conversion?

The parent width is the width of the containing element in pixels. For example, if you're setting the width of a div inside a container that's 1200px wide, the parent width is 1200px. Percentage values are always relative to this parent width—50% of a 1200px container is 600px, but 50% of a 800px container is 400px.

Can I use percentage for height in CSS?

Yes, but percentage heights work differently than widths. For percentage height to work, the parent element must have an explicit height set. Unlike widths, percentage heights don't work when the parent's height is auto. For vertical spacing, consider using viewport units (vh) or flexbox/grid layouts instead of percentage heights.

Should I use percentage or viewport units (vw)?

Use percentage when you want elements to scale relative to their parent container. Use viewport width (vw) when you want elements to scale relative to the entire browser window. Percentage is better for nested components and grid layouts, while vw is useful for full-width sections and typography that scales with screen size.

How do I convert percent back to px?

To convert percentage back to pixels, multiply the percentage value by the parent container width, then divide by 100. The formula is: px = (% × parent width) ÷ 100. For example, if you have 50% of a 1200px container: (50 × 1200) ÷ 100 = 600px. This reverse conversion is useful when you need to calculate exact pixel dimensions from percentage-based layouts.

What is the default parent width if not specified?

In CSS, if no explicit width is set on a parent container, block-level elements default to 100% of their parent's width, which ultimately traces back to the browser viewport width. For accurate px to percent conversion, you should always identify the actual computed width of the parent container. Use browser developer tools to inspect the element and find its computed width value.

Can I use CSS calc() with percentages?

Yes! The CSS calc() function is extremely powerful when working with percentages. You can mix units like width: calc(50% - 20px) to create flexible layouts with fixed spacing. This is particularly useful for grid systems with gutters or creating responsive designs that need precise pixel adjustments within percentage-based layouts.

How does box-sizing affect percentage width calculations?

The box-sizing property significantly impacts percentage widths. With box-sizing: content-box (default), percentage width applies only to content, and padding/borders are added on top, potentially causing layout overflow. With box-sizing: border-box, the percentage includes padding and borders, making calculations predictable. Always use border-box for percentage-based responsive layouts to avoid unexpected width issues.

What's the difference between % and vw for responsive design?

Percentage (%) is relative to the parent element's width, while viewport width (vw) is relative to the browser window width. Use % for component-level responsiveness where elements adapt to their container size. Use vw for page-level responsiveness where elements scale with the entire viewport. For example, a sidebar might use 25% to stay proportional to its container, while a full-bleed hero section might use 100vw to span the entire screen width.

Related Tools

PX to EM

Convert pixels to EM units

Relative to parent font size

PX to REM

Convert pixels to REM units

16px = 1rem (default)

PX to PC

Convert pixels to picas

1pc = 16px (96dpi)

PX to PT

Convert pixels to points

1pt = 1.33px (96dpi)

Try Our PX to Percent Converter Now

Convert px to percent instantly with our free calculator. Start building more responsive and fluid layouts today.

Use PX to Percent Converter