PX to Percent Converter
Convert between Pixels (px) and Percentage (%) CSS units with customizable parent font size
Live Font Size Preview
Hello
Conversion Formula
How Pixels and Percent relate to each other
PX → %
% = (px ÷ parentSize) × 100
e.g. (16 ÷ 16) × 100 = 100%
% → PX
px = (% ÷ 100) × parentSize
e.g. (100 ÷ 100) × 16 = 16px
Percent is always relative to the parent element's font size. Change the parent size in Settings to match your context.
CSS Style Properties
Pixel value
h1 {
font-size: 16px;
}Percent value
h1 {
font-size: 0%;
}PX to Percent Conversion Table
Parent font size: 16px
| Pixels (px) | Percent (%) |
|---|---|
| 4px | 25% |
| 8px | 50% |
| 12px | 75% |
| 16px | 100% |
| 20px | 125% |
| 24px | 150% |
| 28px | 175% |
| 32px | 200% |
| 36px | 225% |
| 40px | 250% |
| 44px | 275% |
| 48px | 300% |
| 52px | 325% |
| 56px | 350% |
| 60px | 375% |
| 64px | 400% |
| 68px | 425% |
| 72px | 450% |
| 76px | 475% |
| 80px | 500% |
About PX to Percent Conversion
What is PX (Pixels)?
PX (Pixels) is an absolute CSS unit representing a single dot on the screen. It does not scale with the parent element or user browser preferences, making it precise but inflexible. It is best used where an exact fixed size is required.
What is Percent (%)?
Percent (%) is a relative CSS unit. For font-size,
it resolves relative to the parent element's font size — 100% means "same as the parent".
It scales naturally with the parent, making it useful for proportional, responsive layouts.
The Conversion Formula
% = (px ÷ parentFontSize) × 100
With a default 16px parent: 8px = 50%, 16px = 100%, 24px = 150%. Change the parent font size in Settings to model a different element context.
When to Use PX vs Percent
- PX: Use for borders, shadows, precise layout spacing, and cases where size must never change.
- Percent: Use for font sizes and widths that should scale proportionally with the parent element.
- For accessible typography, prefer percent (or em/rem) over px so text scales with browser zoom and user preferences.
Common Conversions (parent = 16px)
8px
50%
10px
62.5%
12px
75%
14px
87.5%
16px
100%
18px
112.5%
20px
125%
24px
150%
How to Use the PX to Percent Converter
- 1
Enter your value
Type the pixel (or %) value you want to convert into the "From Value" input field.
- 2
Select the unit direction
Choose px or % in both dropdowns. Use the swap button to reverse direction instantly.
- 3
Set the parent font size if needed
Click Show Settings to change the parent font size. This is the px value that 100% resolves to in your context.
- 4
Read the result and copy
The converted value appears instantly. Click Copy to copy it to your clipboard.
- 5
Check the live preview and table
The Live Font Size Preview shows how the result renders. The table lists common px values and their percent equivalents.
Tip: With the default 16px parent, dividing any px value by 16 and multiplying by 100 gives you the percent. For example: 12px ÷ 16 × 100 = 75%.
Common Use Cases
Responsive Typography
- • Convert a fixed px font size spec to percent for scalable typography
- • Replace px font sizes with % in CMS theme stylesheets
- • Calculate the percent equivalent of a designer's px specification
Accessibility Improvements
- • Migrate px font sizes to percent for browser zoom compatibility
- • Ensure text scales with user browser font preferences
- • Convert WCAG minimum size recommendations from px to percent
Layout & Width Calculations
- • Convert a fixed px container width to a percent of the parent for fluid layouts
- • Calculate percent-based column widths from a fixed-width grid design
- • Convert px padding or margin values to percent for proportional spacing
CSS Framework Migration
- • Convert a px-based Bootstrap layout to percent-based fluid grid
- • Migrate fixed px typography from an older stylesheet to percent
- • Translate px design tokens to percent for a new design system
Email Template Development
- • Convert px font sizes to percent for email clients that require relative units
- • Calculate percent widths from fixed px table cell dimensions
- • Verify that px sizes in the design match a sensible percent value
Learning & Teaching CSS
- • Understand how percent font sizes relate to fixed px values
- • Demonstrate the impact of changing the parent font size on percent values
- • Use the live preview to explore font size changes interactively
Frequently Asked Questions
What is the formula to convert px to percent?
% = (px ÷ parentFontSize) × 100. With a default 16px parent: 8px = 50%, 16px = 100%, 24px = 150%. Change the parent size in Settings if your context differs.
What does the parent font size represent?
For font-size, percent resolves relative to the parent element's font size — 100% means "same as the parent". The default is 16px because that is the browser's default root font size. Set it to match your element's actual parent size for accurate results.
Why convert px to percent instead of rem?
Both achieve relative, scalable sizing. Percent is useful when sizing should be relative to the immediate parent element. REM is better when you want consistency regardless of nesting depth. For layout widths (not font sizes), percent is often the more natural choice.
Does percent work for properties other than font-size?
Yes, but the reference point changes. For width and padding, percent is relative to the parent's width. For height, it is relative to the parent's height. Set the "parent font size" field to the relevant parent dimension for accurate px-to-% results in those cases.
How do I convert percent back to px?
Use the swap button, or apply: px = (% ÷ 100) × parentFontSize. For 75% with a 16px parent: (75 ÷ 100) × 16 = 12px.
Is my data safe? Does this tool send data to a server?
No data leaves your browser. All calculations happen entirely client-side using JavaScript. Nothing you enter is uploaded or stored anywhere.
What is the difference between percent and rem?
Percent is relative to the parent element's value, while REM is always relative to the root html element's font size. Percent can produce different results at different nesting levels; REM is consistent everywhere on the page.
Is 16px always equal to 100%?
Only when the parent font size is 16px. If a parent element has font-size: 20px, then 100% = 20px and 16px = 80%. Use the Settings panel to adjust the parent size to match your specific context.