PX to Percentage Converter
Convert pixel values to percentages for responsive and fluid layouts
PX to Percentage Calculator
Percentages in CSS are always relative to another value. For width/height, percentages are relative to the parent container's size. Enter both the pixel value and what it should be a percentage of.
Conversion Result
Common Percentages
Click any of these common percentages to see their pixel value based on your container size:
Batch Converter
Convert multiple pixel values at once. Enter values separated by spaces, commas, or new lines.
Batch Results
| Pixels | Percentage | CSS Code |
|---|
Common Use Cases for Percentages
Percentages are particularly useful in the following scenarios:
| Use Case | Percentage Values | CSS Example |
|---|---|---|
| Fluid Width Layout | 100%, 50%, 33.33%, 25% | .container { width: 100%; } |
| Two Column Layout | 50% (or 48% with gap) | .column { width: 48%; margin: 0 1%; } |
| Responsive Images | 100% (max-width) | img { max-width: 100%; height: auto; } |
| Flexible Padding | 5%, 10% | .card { padding: 5%; } |
| Grid Systems | 8.33% to 100% (12 columns) | .col-6 { width: 50%; } |
| Centered Element | 50% + transform | .center { left: 50%; transform: translateX(-50%); } |
| Aspect Ratio | 100% + padding-bottom | .ratio-16-9 { padding-bottom: 56.25%; } |
Frequently Asked Questions
In CSS, percentages are always relative to another value, but what they're relative to depends on the property being used:
- Width/Height: Relative to the parent element's width/height
- Padding/Margin: Always relative to the parent element's width (even for top/bottom)
- Font-size: Relative to the parent element's font size
- Transform: Relative to the element itself
- Top/Right/Bottom/Left: Relative to the parent's height (top/bottom) or width (left/right)
- Background-position: Relative to the difference between the element and image size
For padding and margin, it's important to remember that both vertical (top/bottom) and horizontal (left/right) percentages are calculated based on the parent element's width, not its height.
Percentage units are best used in the following scenarios:
- Fluid Layouts - When you want elements to scale proportionally with their container
- Responsive Design - For layouts that need to adapt to different screen sizes
- Grid Systems - When creating column-based layouts that need to fill a container
- Content That Needs to Scale - For elements where the width-to-height ratio should be maintained
- Variable Content - When you don't know the exact size of the content but want to allocate a proportional space
Fixed units like pixels are generally better for:
- Borders and small UI elements
- Typography (although rem is often preferred)
- Elements that should not scale with their container
- When you need pixel-perfect precision
A common approach is to use percentages for layout and structural elements, while using pixels or rem units for typography and UI details.
To calculate a percentage value manually, use this formula:
For example, if you want a div to be 300px wide inside a 1200px container:
Percentage = (300 ÷ 1200) x 100 = 25%
For common fractions, here are the exact percentages:
- 1/2 = 50%
- 1/3 = 33.33%
- 2/3 = 66.67%
- 1/4 = 25%
- 3/4 = 75%
- 1/5 = 20%
- 1/6 = 16.67%
- 1/8 = 12.5%
- 1/10 = 10%
- 1/12 = 8.33%
Here are some best practices for working with percentage-based layouts:
- Be aware of padding and borders - These can affect the overall width when using the default box-sizing. Use
box-sizing: border-box;to include padding and borders in the width calculation. - Account for gutters - When creating multi-column layouts, remember to account for margins/gutters. For example, two 49% columns with 2% margin between them.
- Set max-width for large screens - Extremely wide elements can be hard to read. Set max-width constraints for better readability on large screens.
- Use min-width for small screens - Very small elements can be unusable. Set min-width constraints to maintain usability on mobile devices.
- Combine with media queries - Use media queries to adjust percentage-based layouts at different breakpoints.
- Test across devices - Percentage-based layouts can behave differently across devices. Always test your designs on multiple screen sizes.
/* Example of a responsive percentage-based layout */
.container {
width: 100%;
max-width: 1200px;
margin: 0 auto;
}
.column {
box-sizing: border-box;
float: left;
width: 32%;
margin-right: 2%;
min-width: 250px;
}
.column:last-child {
margin-right: 0;
}
@media (max-width: 768px) {
.column {
width: 100%;
margin-right: 0;
}
}
About Percentage Units
Percentage units in CSS are relative values that allow elements to scale proportionally to their parent container. This makes them essential for creating fluid, responsive layouts.
Benefits of Percentage Units
-
Fluid Layouts: Elements scale with their container
-
Responsive Design: Adapts to different screen sizes
-
Proportional Spacing: Maintains consistent proportions
-
Device Independence: Works across all device sizes
Percentages have been part of CSS since the beginning and are supported by all browsers, making them a reliable choice for responsive design.
CSS Usage Examples
Common ways to use percentage units in your CSS:
/* Fluid layout */
.container {
width: 100%;
max-width: 1200px;
margin: 0 auto;
}
/* Multi-column layout */
.two-column {
display: flex;
flex-wrap: wrap;
}
.column {
width: 48%;
margin-right: 4%;
}
.column:nth-child(2n) {
margin-right: 0;
}
/* Responsive image */
.responsive-img {
width: 100%;
height: auto;
}
/* Creating aspect ratios */
.video-container {
position: relative;
width: 100%;
height: 0;
padding-bottom: 56.25%; /* 16:9 aspect ratio */
}
.video-container iframe {
position: absolute;
width: 100%;
height: 100%;
}Use box-sizing: border-box; to make percentage widths include padding and borders.