PX/REM Conversion - Toolkk

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Tool Introduction

The PX/REM online converter is a practical tool designed for front-end developers and designers. It helps users quickly convert CSS pixel (PX) values to REM units and vice versa, greatly simplifying unit conversion in responsive layouts. By flexibly customizing the root font size (base), this tool ensures the accuracy of conversion results and consistency with the project. Whether for mobile adaptation, web layout design, or daily CSS unit calculation, the PX/REM converter provides convenient and efficient service, effectively improving your front-end development efficiency.

How to Use

In the "Pixel (PX)" input box, enter the pixel value you need to convert. The default value for this field is 1, which you can modify according to your actual needs.
In the "Root Font Size" input box, set the root font size (in px) used by your project or page. This value defaults to 16px and is a key benchmark for calculating REM. Please ensure it is consistent with your CSS settings.
The system will automatically calculate and display the corresponding REM value in the "REM" output box based on your entered pixel value and root font size.
If you need to perform a reverse conversion from REM to PX, you can directly enter the REM value in the "REM" input box, and the tool will automatically calculate and display the corresponding PX value based on the set root font size.

PX/REM Conversion Formulas

REM is a new relative unit added in CSS3, whose value is relative to the font size of the HTML root element (html). Mastering the following calculation formulas will help you better understand and use this tool:

PX to REM Formula: REM = Pixel Value (PX) / Root Font Size (Base Font Size)
REM to PX Formula: Pixel Value (PX) = REM Value * Root Font Size (Base Font Size)

Usage Examples

The following examples will demonstrate how to use this tool for PX and REM unit conversion:

Example 1: PX to REM (Default Root Font Size)
- Input Data:
  Pixel (PX): 32
  Root Font Size: 16px
- Operation Demonstration: Enter 32 in the "Pixel" input box, and keep "Root Font Size" at the default 16.
- Expected Output:
  REM: 2rem
Example 2: PX to REM (Custom Root Font Size)
- Input Data:
  Pixel (PX): 48
  Root Font Size: 10px
- Operation Demonstration: Enter 48 in the "Pixel" input box, and change "Root Font Size" to 10.
- Expected Output:
  REM: 4.8rem
Example 3: REM to PX (Reverse Conversion)
- Input Data:
  REM: 2.5
  Root Font Size: 16px
- Operation Demonstration: Enter 2.5 in the "REM" input box, and keep "Root Font Size" at the default 16.
- Expected Output:
  Pixel (PX): 40px

Frequently Asked Questions

Q: What is Root Font Size?
A: Root font size refers to the font size set for the root element of an HTML document (<html>). In CSS, the REM unit is calculated relative to this root font size. For example, if the root font size is 16px, then 1rem equals 16px. It is a key factor in achieving responsive layouts and font adaptation.
Q: What input formats does this tool support?
A: This tool primarily supports numerical formats for pixel (PX) values and root font size. You can also directly enter REM values in the REM input box for reverse conversion. All input boxes support positive numbers and decimals.
Q: What is the format of the output results?
A: The output results are displayed in numerical form, with PX results including the px unit and REM results including the rem unit, making it convenient for you to directly copy them into your CSS code.
Q: Are there any usage restrictions?
A: Currently, there are no strict usage count or feature restrictions. As long as the entered pixel value, REM value, and root font size are valid positive numbers (decimals supported), the tool will function normally.

Notes

The entered pixel value, REM value, and root font size must be positive numbers and can include decimals. Please ensure the validity of the input data to obtain accurate conversion results.
The root font size is a critical parameter for PX and REM conversion. Please be sure to set the "Root Font Size" correctly according to your project's CSS styles or design specifications, otherwise the conversion results may not match your expectations.
The browser's default root font size is usually 16px. If your CSS does not specifically set html { font-size: ... }, then using 16px as the baseline is a common practice.
This tool only provides unit conversion functionality; you need to manually copy and apply the generated CSS code to your project.

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