PX to REM Converter
Convert pixel values to rem units easily.
In modern web interface development — especially when aiming for responsive and accessible design — understanding how different units of measurement affect layout behavior is essential. The pixel (px) is still widely used by designers in prototyping tools, where visual accuracy is the main focus. However, when designs are translated into code, relying on absolute units like pixels can cause issues — particularly in environments with zoom-based accessibility settings, high-density displays, or custom user preferences. This is where rem comes into play: a relative unit based on the root element’s font size (<html>), enabling developers to build interfaces that are more flexible, scalable, and accessible.
🧮 How the PX to REM Converter Works The conversion is based on a straightforward formula, but its accuracy depends heavily on the base font size defined in the HTML document. General formula:
rem value = px value / base font size
By default, most browsers set the root <html> font size to 16px. So, for example, 32px equals 2rem. However, this base value can be changed via CSS, which alters the entire scaling logic. Our tool uses 16px as the default but allows users to input a custom base size, making the converter more versatile and adaptable to real project scenarios.
🌍 Standards, Evolution, and Historical Context Relative units like rem were introduced to address the growing need for more adaptable and accessible interfaces. In early CSS, the em unit already provided proportionality, but since it was based on the parent element’s font size, it caused inheritance and nesting issues. The rem (short for “root em”) solved this by always referencing the root <html> element. Today, rem is recommended by W3C as a best practice for responsive and accessible layouts. Meanwhile, the pixel has evolved. Originally tied to physical screen dimensions (like 1/96 inch), it is now treated as a logical unit — often referred to as a “CSS pixel” — standardized across browsers for visual consistency on different devices.
🧠 Technical Insights on Pixel and REM
- The word “pixel” comes from picture element, the smallest addressable component of a digital image.
- 1rem = 16px only holds true if the root <html> has font-size: 16px. Changing this alters the scale entirely.
- Using rem allows developers to scale the entire UI by modifying just one value — the root font size.
- Modern browsers let users increase default font sizes, which directly affects rem-based layouts, but not pixels.
📊 PX to REM Conversion Table (Base 16px)
| Pixels | REM |
|---|---|
| 1px | 0.06rem |
| 2px | 0.13rem |
| 3px | 0.19rem |
| 4px | 0.3rem |
| 5px | 0.3rem |
| 6px | 0.4rem |
| 8px | 0.5rem |
| 10px | 0.6rem |
| 12px | 0.8rem |
| 14px | 0.9rem |
| 15px | 0.9rem |
| 16px | 1rem |
| 18px | 1.1rem |
| 20px | 1.3rem |
| 24px | 1.5rem |
| 25px | 1.6rem |
| 28px | 1.8rem |
| 32px | 2rem |
| 36px | 2rem |
| 40px | 3rem |
| 44px | 3rem |
| 48px | 3rem |
| 50px | 3rem |
| 56px | 4rem |
| 64px | 4rem |
| 72px | 5rem |
| 75px | 5rem |
| 80px | 5rem |
| 90px | 6rem |
| 100px | 6rem |